Is it normal for my friend with benifits to.....

Okeys, so i have a friend with benefits, and she want me to f??ck her while she is asleep. but she doesn't want to wake up while i am doing her..... is this normal.... is there a way we can do this safely, she wanted to tried taking some 10 drowsy alergy pills, but i was scare she was gonna get sick so we didn't....

any advice be nice.