i’m a lesbian and have encountered this many times before. often times, when you come out to someone who is questioning their sexual orientation, they’ll latch onto you. not just because you’re out but probably because they’re attracted to you. if she has questioned her orientation, she’s possibly looking for a way to express that further. that she’s married and that you’re not interested are two big problems though.
some women are just really flirty though, so it’s good that you’ve identified it going over the boundary of what’s comfortable for you.
in this case, because it’s gone on for so long, I would say to be direct with her and say something to the effect of, “I know that I could be wrong with this, but because you’re my friend I wanted to bring it up. I’ve been feeling like there’s more than just friendship happening here and that’s making me feel uncomfortable. I wanted to address it because I want to continue our friendship but I need to know that this elephant in the room (or at least what feels like it) was dealt with. I want to stay friends and want to keep our friendship at a platonic level, but was wondering what your thoughts were on this subject.”
…could be awkward, might not be though. Always worth asking about. In the long run, it’ll save a lot of grief and possibly the friendship :)