I'm kind of confused about this also. The last time me and my love hung out alone was a month or so ago and he was talking about how his gf was always picking fights with him and always pointing the bad out and never the good in him. I changed the subject because I felt like it wasn't my place to comment on their relationship and I didn't want to give their relationship any energy....but then on the other side of it, what if this is the universe aligning stuff for you??? 

I guess I'd say to be there for her but still try and not give the other guy energy. Like speak to her in a way that she knows you're there for her but try and not bring him up as much as you can so that you're not giving him energy or relevence....but someone else here may have a better answer for you....I'm a little unsure myself...