The particular challenge you face—as it seems to me—is that you don't yet know your character.
That's an apt summation...I know her personality and some of her biographical sketch but I've been struggling for a long time over what sort of life experiences she might have had that would drive her to make the choices she makes in the story, outside of the things that happen in the story. She is young (19) and middle class so she hasn't had a lot of time or pressure to have them; when danger comes knocking her initial reaction is about what you'd expect of someone from that background.
Pretty sure the OP was using the term to distinguish from Native American. I believe there are more accurate terms that can be used here, though. Sounds like the MC is also American by birth, which means the mountain of research might still qualify as a hill.
This - not Native American. But also leaning toward Hindu-influenced background as opposed to Muslim. The fact that there are also many Indian ethnicity was one of the things I ran into within about five minutes of digging into Ari's links. In the current draft she is non-religious though she does end up interacting with the religions of the cultures she runs into and changing her religious background would change how she sees them; I'm fine with that.
That said, I'm going to come down on mccardey's side. "Adding ethnicity" isn't... really a thing, IME. You can change the race of a character, but it involves a lot more than putting some makeup on them or even (and I agree it's worrisome that you want to avoid this) changing their last name. It also concerns me that you're looking at it from a place that this will add "flavor" to her. Put that way, it gives the image that ethnicity is a pizza topping to be added or removed at will, which is a problematic way to view a part of the character's identity.
Flip side... Oh yeah, "Mighty Whitey" is a hugely problematic set of tropes, that concerns me whenever I see it. And I understand you don't want to change the book's plot, or set it somewhere less controversial. So in that respect, I would come down on the side of "Write a POC main character." I'm saying it that way, not "make her a POC," because if you go this route, you'll be reworking a lot of her. You may find in the course of your research that a lot of her life and personality won't change--but you'll have to examine it to be sure. If she's living in this area as the child of those immigrants working in tech jobs, she's going to have a very different view of the area than the child of one of the white families that (just an example, I have no idea where she lives) lived there since the Great Depression.
Disclaimer: I'm probably whiter than the OP.
Just out of curiosity, could you have the MC's family come from the real-world+modern equivalent of your fantasy setting?
Ok, I dramatically simplified the setting description so I'll explain it and why I came to the decision to make Earth her origin. This is portal/multiverse setting. Every place in the multiverse is part of the real world and there are potentially infinite combinations of what constitutes "humanity" on any given one (though worlds closer to each other in the fabric of hyperspace tend to share similarities). Worlds that are aware that they are part of that multiverse have alliances and conflicts and every diplomatic combination in between; think of it like interstellar societies except to get to the next world over you walk through the nearest portal or natural tear in hyperspace. (The ability to be sensitive to and control these forces is the scientific-flavored "magic" of the world).
Tara falls through a portal on her homeworld into not the African-influenced world (specifically, a region of it called the Waeru Valley and a city in it called Xalidar) but a European-influenced one (the city state of Remairhey). The place she lands is a member of one of those multi-world alliances (if you read my Sissyfus this year, it's the same one: the Society of Travelers); a sort of inter-dimensional United Nations. She's helped by people who know what to do when a confused person from another world falls into theirs out of apparently thin air. What should have been a nice day tour of the local city to keep her entertained while the Society figures out how to get her home turns into a nightmare when the public square is attacked by a raid of slavers from the Xalidar. Having nearly escaped being killed, Tara is now a material witness and because of newly-discovered affinity for the aforesaid magic (along with personal reasons I'll gloss over for now) she ends up joining the rescue party (which includes an exile from the.
So that's a lot to process and we haven't even gotten to Xalidar yet. The oldest draft of this story that exists opened on Earth but the story really starts when she falls through the portal. When I restarted the story a couple years ago, I gave her an "earth-like but not necessarily Earth" origin but this got frustrating quickly as I kept writing in vague allusion and unspecific detail. Eventually I gave up on this and decided to make it Earth after all; she is there as the point of view character and the person the reader relates through, the story doesn't actually spend a lot of time on her at home and there's just not enough space to develop a third constructed world for her origin.
There are possible future stories in this multiverse; stories focusing around the origin and operation of the Society, stories focusing on the aftermath of this one in the Waeru kingdom and possibly stories of Tara becoming the Society's point of First Contact for Earth.
Is her ethnicity going to be a major component/driver of her character/identity and how she interacts with the fantasy world? I think there's nothing wrong with trying to avoid the white savior trope - but if you are going to incorporate her ethnic background I think it needs to be as more than an incidental "lustrous olive skin and deep brown eyes" physical description.
If you could change that physical description to any race and not impact the rest of the book then I think doing it doesn't work - and if she is mixed (disclosure - I'm mixed), then there is a particular identity in being mixed - of more than one culture/world, not truly belonging to one in particular. If she's mixed and never felt at home in the Indian culture but was never welcomed in white culture - that could play in to her actions/attitudes when she is suddenly a goddess figure in the fantasy world.
Yeah, I did gloss over a lot in my post, but she is the point of view character and changing her background would obviously change how she thinks about things. Some of the reading I did last night suggested some possible background hooks that would mesh with her existing story and personality really well though.
Ok, time to get personal for a bit and I think this might be one of the sources of my struggle with Tara's character: While I grew up white in a majority-white area I was ostricised and bullied because I was singled out as gifted early on. So my perspective growing up is closer to that of an outsider than not (and I used to be frustrated when I went to college and took classes in the social sciences and have people insist that having had the privilage of being white meant I couldn't
really understand what it meant to be Other...a topic I understand with much more nuance over a decade later). What I had been trying to imagine for Tara was the sort of high-school life I never had: someone who joined sports teams and had a steady group of "average" friends and not many life-changing stresses and delt with typical teenage problems and for whom the main thing defining her current life before the story is that she isn't entirely sure what to do with hers. And there are many areas where I've drawn little but blanks. But within a short time of thinking of her as someone a little bit Other and reading about that background, things to fill many of those blanks started suggesting themselves...things that would have to be double checked against my own sterotypes and biases I'm sure but more than I had before. I can immagine what her mother and father might be like, how they might have tried to raise her, how she's experienced culture clash (a major theme of the story) in the past, why she might empathise with certian other characters where before I was having trouble expressing reasons beside "because she's that kind of person".
There's also a question of just how ethnic a POC character actually is. If you're talking a third or fourth generation South Asian (which is another term for people from India) who has been living entirely in the USA, then there's a chance that this person only has minimal "ethnicity" and largely lives a life identical to the average white American. On the other hand, if your character's family had drilled in some semblance of familiarity to the Hindi or Tamil culture that is your character's heritage, then there's a question of just how familiar even they are with it. I'm Canadian, but of Asian ethnicity, and I know a TON of other Asians that only speak a smattering of their native language, and are only familiar with their homeland and culture as a result of an occasional family holiday observation, or one or two trips to the Motherland, and otherwise know Klingon culture better than they do their ancestral one. Person of color doesn't always mean Person Deeply Ingrained With Culture Of Ancestral Origin.
Yeah, I think it's likely that having been born American she would be very Americanized. I can't say yet how much of her parents would have rubbed off on her yet. My inclination is to have her mother be from India and her father to be white; her mother a practicing Hindu and her father a lax Christian and for Tara to not be really dedicated to either (with her parents not wanting to push her) but moderately pulled more toward her mother's faith.