Oh, FFS she's trying to keep the bathroom mirror from fogging up. And she may not even be noticing the body proximity/truly minor contact.
Do yourself, her, her boyfriend, and anyone you date a favor and put it out of your mind.
She's got a boyfriend. If she doesn't want to see him anymore, she'll break up with him. Since she hasn't, your operative assumption is that she wants to keep seeing him-- just like it would be if she was any other woman you meet.
Is she a good roommate? Does she pay her share of the bills, clean her share of the apartment, and not take your food or borrow your things without asking?
If so, then it's a good roommate situation. Don't **** it up by trying to turn it into something that it's not.
Signed, a woman who has lived with men platonically.