in my experience, no, she didn't get better, she got worse. also, use your anxiety and pain as a guide--if she were truly better and communicating this way a lot of this would go away. even though if you never got back together, you'd have to grieve the ending of the r/s, there wouldn't be so much pain and anxiety if all of the sudden she was acting like a person with integrity.
and yes, the posts she accidentally-on-purpose leaks through are there on purpose. next time you see them realize this.
i do think at this point you are experiencing fantasy/delusion -- this is leftover feelings from what they presented themselves to be, but were not. it's normal to feel this way, and 6 weeks is not much time at all--it will take many more months to process everything so don't think that you are weaker than anyone else. best of luck to you!