SUBREDDIT: r/relationships
TITLE: What the hell should I(27/M) do with her(28/F)?
POST: A little background.

Dated a friends coworker for a year back in 2010 and things ended due to the lack of sex(her religious reasons). I end things abruptly over the phone and go no contact. She sends texts every once and a while asking how im doing etc... but I never respond.

Fast forward three years and I get a random text from her saying she just saw me walk into a bar and wants to know if she can come say hello. I don't know why I agreed but she came and we hung out for a bit. We end up going out to eat a couple weeks later to catch up and it turns out she got a boyfriend a couple months after we stopped talking and has been with him since.

Long story short, we've been hooking up behind his back since June. She keeps telling me how unhappy she is in her relationship and how good we are together, etc... I've always liked the girl and I still do. She's fun and is a hard worker and has a career. Sex is great too.

But she won't make a decision. It has been five months and she keeps saying she is about to do it but its getting harder to believe. She has told my best friend, her old coworker, that we are talking again. Am I the backup guy or is he? Should I just stay away? Am I a scumbag?
TL;DR: 
Been seeing old flame for couple months. She has BF who she says she doesn't love anymore and is trying to break it off with but hasn't for several months. Should I run or force her to break up with her BF?