I could be totally off here but the first thing that came to my mind when I read that was: hey maybe she needs to feel a little threatened by another woman in your life? Maybe she sees you as the 'ole reliable' who'll always be there for her if her plans didn't work out? Of course, she could just be slowly drawing towards you and not really ready to commit yet.
Me: 35|WAW: 38|D: 6yo | http://tinyurl.com/2dxx7m6 Feb 2006, left, came back in two weeks Aug 2006, left again Apr 2007, filed for divorce Dec 2007, reunited Mar 2010, moved out, filed again
