She just went through a rough time and I'm sure that in the month she hasn't fully gone out of it yet. She is still running it through her head. A lot is probably going through her head right now and one of the big things is probably a fear of losing a good friend. I can't tell you for sure b/c I don't know how close you are, heck you might not even know how much you mean to her.
In my own experience I went through a very hard time about 2 1/2 years ago and I met someone that is now a very good friend. Then in the spring through the summer more things just started going wrong, but he was always there, even when it was very hard for him to be able to be there. I don't think he has any idea how much he means to me b/c he probably doesn't think he really did anything for me. But I lookup to him and respect him more than any guy I know and care about him very much because of who he is and how he has proved to be one of the most caring and truest friends I have and will ever have.
You could be the same thing to her, or something very similar. And the fear of losing that guy is overwhelming, sometimes enough to make you wary of letting them be more b/c what if it doesn't work out and you care about them more you lose more - also she probably thinks you're a good guy and a good friend, getting closer shows you more of a person, she could be afraid of finding out your not who she thinks you are, just like that guy she just got out of a relationship with, I'm sure she didn't think when it started he was going to drink so much or cheat on her.
I would say that talking about it is always the best option. You can find he right time for the conversation, but you should tell her if you are willing to wait for her, but if in order to wait you need to know the truth you need to ask for it. Be polite and don't force it. tel her she doesn't have to tell you right then but that you want to know if she is just putting you off because you don't feel that way about you, if she really doesn't know how she feels, or if she wants to go out on a date, but she just isn't ready. Say something along the lines that you are interested bu you won be hurt if all she wants is friendship that you just want the honest truth. I would say that it is the last but only the two of you can figure it out and you need to do it together. Good luck :)