Have you ever asked her how she knows you or asked your mutual friends who she is? Maybe you met her, but she didn't make much of an impression on you even though you made a big impression on her.
I don't accept friend requests from strangers. I do have a few industry professionals that I haven't actually met, yet, but hope to work with. FB is a good place to network.
If she's touched something in you try to get to know her better.