I was at my current partners birthday party and a mutual friend (30yo F) came up to me with a haunted expression and said “idk if you know but your ex is dating my ex(32yo M)”. They went on to explain that he made her a horrible person during their time together and just kept repeating “he’s really bad” with the most serious expression. She then said “your ex seems like a nice person, if you care about her at all you have to warn her”.
So my question is, what’s my obligation here? Wouldn’t it come off with little merit having your ex bf tell you your current bf is bad? I want the best for her, she’s a great person, we harbor no ill feelings towards each other and have been separated 1.5 years after a 14 year relationship. I would begrudgingly say something if necessary but I personally don’t want to be involved in that. Should I meddle in this mess and tell her?