What should you do to treat a virgin girl?

Treat? I assume you mean to lose her virginity.

Well, first you need to know whether she wants to lose her virginity. As a biromantic asexual, I don't want to have sex at all or lose my virginity because I just don't want to.

If she wants to let you "treat" her then you can if you want, but keep in mind:

Not everyone wants or needs to be "treated" for something that is not a problem.