I agree, infertility is not the same as being unable to carry to term. With infertility, you can't get pregnant in the first place. With the latter, you can get pregnant, but you just can't stay that way. Under those circumstances, you'd probably need to consider a means of contraception to prevent pregnancy, since you wouldn't want to risk a spontaneous abortion (miscarriage).
There are plenty of reasons why a woman may decide it's not wise to get pregnant, but it's always possible to adopt, use a surrogate, etc. For example, I've chosen not to have a baby because, for one, I have a broken tailbone, which healed in an L-shape, bent inwards toward my uterus. Doctors told me that if I had a baby, the tailbone would have to be re-broken prior to delivery, otherwise the baby might get stuck on its way out. For another thing, I'm on several medications that could pose a risk to a developing fetus, but it would cause me problems if I went off them for nine months, plus however long I chose to breastfeed. Also, I have several medical conditions that are hereditary, and I wouldn't want to pass them on to an innocent child. So, after careful consideration, my husband and I decided to not have kids. If it wasn't for my poor health, we might've considered adopting, but the truth is, I don't have the necessary energy to raise a child.
Now, in my case, I was told it would be difficult, at best, for me to get pregnant, because I have such an irregular cycle. Without my birth control pills regulating things, I might have a period after just two weeks, or none at all for six months. It's totally random! When I stopped taking my birth control pills in order to switch to a different brand, I was supposed to wait so many days after my period began, and then start taking the pills. Well, I waited . . . and waited . . . and waited . . . and after five months or so, I still hadn't had a period, so my doctor had to give me a hormone pill that sort of jump-starts your cycle, forcing you to have a period. Otherwise, I never would've been able to start the new birth control pills.
Now, I'm not a doctor, but I'm pretty sure an appendectomy wouldn't cause scarring to the uterus. Not unless it was botched by someone with no knowledge of anatomy. I had my appendix out when I was ten, and the doctor took a peek at one of my ovaries and told me that they were developing, so I would likely be starting my period within a year or two. So it's possible to look at the reproductive organs while performing an appendectomy. But ovaries are off to the sides, apparently not that far from where the appendix is, so it's not that much of a stretch. The uterus is farther down and in the middle, as I recall, so it'd be a lot harder to cause damage there. You shouldn't need to cut through it to reach the appendix, so there'd be no cause for scarring. (And btw, an appendix scar is pretty small. I had mine done in the 80s, before laparoscopic surgery was developed, and my scar is only about 2" long. I'd imagine that with modern tech, it would be a lot smaller than that. My gallbladder scars from two years ago are about 1/2" long each, there's three of them on the side of my ribcage, plus a 1" scar that emerges from my belly button. Almost invisible.)
You could research other causes of infertility and inability to carry a baby to term. There are some immune disorders that cause the body to attack the fetus, as if it was a foreign invader, which inevitably ends in miscarriage. There's treatments that can help, but it's still risky, from what I understand. A woman might well decide to avoid pregnancy in that case. Then there are things that cause the inability to conceive, like endometriosis, fibrous scarring, cysts, the absence of ovaries, etc. An accident could cause it, too. Say she needs a hysterectomy due to the accident, a branch stabbed through her uterus, causing uncontrollable bleeding, so they had to remove the uterus to save her life. Or maybe she has a tumor or cysts that require the removal of both her ovaries, which they might discover if she collapses while skiing. That would cause her to become infertile.
Lots of possibilities!