Ah.Also "Clitoral Atrophy" isn't a birth defect. It's just something that can happen due to a lack of arousal and use. The clitoris shrinks and "disappears".
Would that happen pre-pubescent, though? The class are first year high schoolers, so that means she's been taking medicine for her mental health since she was about 7 if her time line is accurate.
Though if it's more common forms of sexual abuse that fucked her up, it doesn't mean it's impossible she was abused BECAUSE she was already mentally ill, worsening her, rather than made ill from said abuse.
The mentally ill are often easy targets for such abuse, after all. And as a kicker, many anti-depressants have strong libido killing effects, which could contribute to the atrophy, especially if she was taking big doses during her development.