For whatever it's worth, this is the closest to a unanimous agreement I've ever seen on this website.
ALL of us have been in a similar situation at one point or another in our lives. I know of no one who came out on the winning end. Cut your losses.
Try this on for size...See if she'll agree to start paying YOUR way on a few occasions. I guaranty she'll disappear so fast you'll wonder if she was ever there in the first place. To her, you look like a debit card.