I am sure someone with more experience will post, but my opinion is that you are walking a very thin line here, and your actions and reactions are critical. Your sitch sounds very similar to mine. My h was in affair with coworker, decided that he wanted to try, promised nc, and started showing some affection. Then he went away one weekend to go out with friends, I got anxious- similar to you- and got in an argument with him that he did not care enough to call and check in. After that he seemed very unsure if he wanted to work on the relationship anymore. The more I pushed for affection, and openess, the more withdrawn he got. Until he was back contacting OW again.
This is such a difficult path you are on right now. My opinion is that you have the right to ask for passwords and transparency, but not much more than that. She probably does not feel the feelings that you want her to feel right now, and the more you push for those feelings, or gestures of those feelings, the less she is going to feel them. I think the only thing you really can do is insist that she stay away from OM, work on yourself and don't focus on what she is or is not doing as far as your relationship goes, and be ready to fully follow through on your plan to end the relationship if she will not be transparent or breaks no contact. I think she feels your neediness right now, which makes her realize that she doesn't really have to worry about you leaving her, which makes her not care as much about the relationship.
