What should I do in this situation with this girl?

So she said she liked me at one point for sure(and I believe that's true), but she told me she has a bf. And now she expects things to be normal. I played along but idk what to do now since I feel weird about this

You're going to have to tell us the situation before we can answer.

I've had personal experience with similar situations so maybe I can help. From what you have said, this girl probably told you that she used to like you because 1) she just wanted to get that off her chest, 2) she secretly wants you to feel bad about it, or 3) she wants you to try to make a move on her even though she has a boyfriend. So let me elaborate...

The first one should be pretty self explanatory. Telling someone you used to like that you used to like them can be a pretty relieving thing. I don't know about you, but anytime I stop liking someone, I usually tell them that I used to like them at some point just because all that pent up energy needs to go somewhere and it's nice to finally let it all go knowing that their response wouldn't change a thing. This girl could be similar and it may just a be a nice way for her to feel relief. However, she should have been more clear if this was her intention. When I do this to my past crushes, I tell them that this is what I'm doing and that my only intention is to tell them that I used to like them without any expectations of them liking me back or rejecting me or whatever. If this were the case, then you should just shrug it off and don't ponder on it. Just feel flattered that at one point, someone did like you therefore you are a desirable and normal person!

The second possible reason is kind of a mean one on her part in that she wanted you to feel bad that you didn't make a move or something while you could have. If this really did make you feel bad, then try not to think about it because there is no use regretting something that "could have been". Also you should think about this as dodging a bullet because you wouldn't want to be in relationship with someone who is immature like this anyway. But if this didn't really affect you in that way, then just move on because obviously she has failed to make you feel bad and there really isn't anything else to it.

The last reason means that she's a rather petty person who is willing to cheat. In this case, you should definitely try to keep your distance.

Since you don't know what her reasons could be, the thing you should do is simply acknowledge that she used to like you and do nothing about it. You could try to keep your distance from her if you feel weird but other than that you shouldn't think of it as a big deal. I think that you mostly feel weird because you're thinking of the "what ifs" or the "could have beens" when really there isn't any need for that. What's passed has passed and if it helps you, pretend that she never said anything.

I say keep your distance. Hang out, but don't be buddy buddy.  She's got a boyfriend after all.

I have a rule of thumb never to get into a relationship with someone who's already in one for two reasons the first is I wouldn't want it to be done to me, and secondly let's say that she eventually leaves this person for you...what makes you think that he or she won't jump on the next best thing? 

These types of people have no understanding of what is and aren't true to themselves, I would make my intentions plain and tell them I am looking for nothing more then friendship. If they agree, fine. If not, keep it moving.