It doesn’t exactly hurt to remind her of the bad times he’s caused, but don’t tear your hair out expecting her to respond to facts alone.
His negative behavior may be at some level the exact thing that attracts her to him.
Unfortunately, in these situations it almost never works to come right out and complain.
Even if you can recite ten or fifteen specific times when he’s acted like a real jerk, doing everything from spoiling family functions to wrecking her credit history, you’ll probably find she’s got a pack of rationalizations to counter all of them.
And things get way too complicated when you know he is bad for her but she seems head over heels in love with him. Don't judge him: The first rule is to act completely neutral else your bestie will think that you dislike him because of your own issues.
You know you have to warn her but you also know how sensitive she is and how this could turn into one big problem. When she talks about their problems, refrain from taking sides rather point out the fact that both of them need to work it out. Point out the fact that most people dislike this relationship: Bring to her notice that the guy she is so in love with hasn't been able to charm anyone else.
This rule is almost never stated or enforced among queer communities.
If you're gay, you will almost inevitably date a friend's ex at some point.
Queers don't tend to expect our dates to come into our lives completely free of prior complication.
She needs to know that people aren't too comfortable with the idea of the two of them dating. Be straightforward: Ask her if this is how she envisioned a perfect relationship when she asks for an opinion. But be sure to not be over critical else she might stop communicating with you altogether. Make her a little suspicious: It isn't fair but then this is war.
Put tiny doubts in her head about whether he is completely loyal to her, or if he feels the same way too.
You slowly drift apart, and the very thing you were trying to avoid (losing her as a friend) happens anyway.
The worst thing to happen to your friend is a jerk boyfriend.