Clairvoyance would be more the ability to see someone's future (or past). Clairvoyance, telepathy, and other mind abilities beyond the normal aren't considered illnesses - more like super powers.
I think there's a whole spectrum of opinions concerning what you call "super powers," besides everyone assuming they're real. While some people accept them as real, others see them as a combination of the various well-documented ways that human beings fool themselves with confirmation bias, magical thinking, and so forth.
I don't think most people would categorize them as a mental illness, unless the belief interfered with a person's everyday life or caused them distress (which apparently is the case with DamaNegra's character when she decides to visit a psychiastrist), but that's still a long way from accepting them as part of our shared reality.
To address the original post, I don't know if this would give some insight, but
Here's a very long, apparently real-life thread, where a poster with the user-name of Brendy begins:
I am hoping to find people here who don't pretend telepathy isn't real. In my experience almost everyone can do it, but never talks about it out loud. I don't understand why.
After many posts, a few months later, Brendy writes back again:
A thanks goes out to all of you. I am on new medication now and it is working wonderfully. I no longer hear new voices, only the older ones and even they are very diminished.
That's all I wanted to say. Just thanks for be supportive.
This sounds similar to the outcome that DamaNegra's character's
hopes for, at the point she visits the psychiatrist. Obviously in a fantasy novel, an author can make the visions be "real" (in the sense that they consistently and reliably convey information the person wouldn't have any other way of knowing) and take it in any different direction.
In that thread, one can see how Brendy definitely believes in what's happening to him/her, to the point that he/she thinks it can be proven in a controlled scientific test, which is why he/she is writing to this particular forum. One can also see the various reactions of other posters, from cruel to helpful, and of course the final outcome as quoted above.
Ditto also to everything Ink Wench said.