tell her
I wish my boyfriend were just honest with me from the beginning...
At first I shaved when I dated him, knowing that a lot of guys prefer it. I asked him if he had a preference, and he said he didn't care. Then when I grew it back, he'd make a big point of pulling hair out of his teeth... Then I asked him again if he wanted me to shave... He was wishy washy about it.
Then, just recently he told me that he thought it was "weird" when I was shaved because I wasn't always 100% completely smooth and shaved, and he hated stubble...
So, I'd say, just be honest with her. Maybe ask her if she wants YOU to shave. Or ask her "Have you every shaved your pussy?" or something like that, "Do you want me to shave you?". It's kind of hard to guess what a guy's thinking unless he SAYS something. But, I guess it has to be in a way that doesn't make the girl feel like an ass like "YO BITCH! SHave that nasty hairy thing!"