My bf doesn't go down on me when I have my period because he doesn't like the taste or smell of a woman's vaginal area when she's menstruating, but he isn't all immature about my period, he just prefers not to be sexually active when I'm bleeding. and that's fine with me, I don't want to have sex when I'm bleeding. but if I accidentally bleed on the sheets, or something like that, he's not disgusted about it. he knows it's natural and accepts it's part of being a woman, and he has a lot of respect for women. but he's a mature man, not a teenage boy, they're very different than a mature man, they're more likely to be immature, disgusted and rude about it.
I have my red wings,I don't really mind so much if she doesn't.If it happens I don't run like a little boy.
It's not a big deal. Like any other bodily function.