These two had 4 years to make a go of their relationship. Instead, it just fizzled. So they were not all that deeply in love. Of course, like any couple they had their happy moments. Four years is long enough for them to have gotten to know each other well. So, now, after a two year hiatus, they both think it might be fun to try the old chemistry again. I doubt they wouldn't just end up with the same problems that caused them to part once before. Like I said above, he may just be looking to see if he can score.

This little dalliance probably won't go far, but it could be very damaging to the trust that you and she need to have to continue what the two have started to build. What she's doing is totally wrong, IMHO.

It does sound like, either, you will have to put your foot down, or this guy is going to be hovering on the periphery of your life. That would be intolerable for you. The person who needs to straighten up is her, not him. She has given this guy a ton of encouragement. So, now, installing appropriate boundaries will be a challenge. Either she has to decide that she's not all that into you, or she should conpletely cut off contact with him. She can't have her cake and eat it too. She has no right to be causing you this pain. You wouldn't do this to her.