TL;DR: started as a friend for a brief time, I'd like to get her. What do?

A very unusual story, I usually do not end up in situations like this. So, I meet this girl and start having conversations with her(we are on the same path to work). Days pass and I ask her to hang out, she catches the door and greets me. For some days I voluntarily do not talk to her and deny her tentatives to reconnect. Since this week, we started talking again and in a conversation I ask her if she is in a relationship and she tells me that she is but it's in crisis. Now she seems pretty receptive to my mild escalates but I do not know how to close this, especially to avoid being an orbiter. What should I do?