I need advice, my best friend is being played

I want to ask advice for my best friend. I am going to tell this story as it was tolad to me. David went to Angel 2 months ago and ask for a divorce, after being married 15 years. (The last 2 years things have been strained between the two of them, with grown kids in the house and her first grandbaby she was always to tired for sexual relations. After he left her, she made the kids move out and her sexual appetitate returned.) They began having relations and a month later he announced he was engaged to a girl he had known from childhood. For a while they snuck around and was together, until I finally convinced her it was not winning him bk. His girlfriend is a truckdriver that is gone for 30 days and home for 5 days. During the 5 days shes home, angel doesnt even hear from david but as soon as she is gone bk on the road he is calling and texting angel again. david has told angel the the relationship only stands a 20% chance of making it, but when she ask why? he says it is not her concern. he also told her that he and his girlfriend wasnt having sexual relations, in case the relationship dont work they can still be friends. also the girlfriend has a male (truck driving ) partner that makes trouble everytime david calls to talk to her. i have told her to move on but she wants him back. I am hoping that some people on here can give her advice on what she needs to do.

Just tell her not to do something she will regret in the future messing up her life