Your girlfriend is right, that she is not at significant risk of strep
from either kissing
you or by oral sex. But her reasons (and
yours) may be the wrong ones. Assuming you and she have been in close contact in the past several weeks, with kissing, having sex, touching, and perhaps sharing eating utensils, kitchens, and toilets, there's a good chance she already is carrying the strep that caused your sore throat.