She sounds like she is mortified by what happened, sometimes, depending on the people around you when you start menstruation you can sometimes end up with complexes, all you can do is be supportive for now, wait a week until the hormones have returned to normal and tell her that you don't want to see her upset like that again,especially over something that happens every woman, and will happen probably happen again in the future,  As a woman I can say this. Tell her it doesn't bother you and you think she needs to cut herself some slack