just my take...but as a waw that took my H for granted during the split I'd say that she could be using you to help her get through the scary period of adjusting to being alone.
Getting to come "home" for a few days and have a closeness with you...even if it's just a very very close friendship gives her that feeling that she isn't just floating out there. She has that security of you, the familiar, the safety net.
I'm just saying me and H when I walked...we said we'd be best friends forever, we'd be one of those couples other people didn't understand, if we weren't married when we were 60 we'd retire where we always talked about, I could go on...and this plan worked great while I got to do what I wanted to do and then come home and make dinner with him, watch tv with him, go places with him. It didn't work so great when he decided that wouldn't be there how and when I wanted him.
