Before, considering any of that, I would give her space if she is planning on breaking up with her partner. Not everyone can just break up and then jump into a new situation. I would be your friend to her, a listening ear, but still keep her in arms length, especially because she isn't single. Even if she did like you, it sounds like something that definitely needs time to develop to understand if the like is genuine or she's just leaning on you for support.