“I have an ex-girlfriend who recently returned to my life. She started seeing someone else while stil asdfadsf ”

I have an ex-girlfriend who recently returned to my life. She started seeing someone else while still with me, and ended up leaving me for him. Their relationship has now ended, and I think we're both pondering trying again at some time soon.nI don't know if I could ever get over the heartbreak she put me through, yet she swears she wishes she could take back her mistake and I definitely still care deeply and think about her a lot. Should we try again? Or is it too great a risk?