I like her and she never told me she had a boyfriend.?

I think you should just avoid the boyfriend thing all together. Meaning, don't get too personal about it. I would bring it up a little. Just be like.. I happened to see on your facebook that you have a boyfriend, I don't wanna jeapordize your relationship with him, so if I am in the way of that then I'll step off a little bit but if not I'd be glad to still be your friend. That shows that you're respecting her relationship status and you're respecting her. She will appreciate that.