First of all, you and she are both doing extremely well to focus on all the ways she is excelling!
Secondly, I think a more helpful diagnostic category to consider would likely be social anxiety (which isn't far off of selective mutism, but I suspect is still a better fit).
She is a strong self-advocate, and, from everything you have shared, has increasingly shown herself to be the person best equipped to make use of diagnostic information about herself (as it should be). She and you might find some of the literature on social anxiety useful in understanding herself and the range of appropriate interventions, even if it doesn't turn out to be a perfect diagnostic fit (NIMH free publication--as a pdf download or order free hardcopy):
https://www.nimh.nih.gov/health/pub...order-more-than-just-shyness/index.shtmlOr this slightly older, but still excellent, first-person account of a very high-functioning adolescent with social anxiety (free pdf download at the Annenberg site--amazon link to hardcopy follows):
https://www.annenbergpublicpolicycenter.org/publication/what-you-must-think-of-me/https://www.amazon.com/s?k=what+you+must+think+of+me
