Make Her Jealous
If you really want to make sure you don't end up in the permanent friend zone after becoming her confidant, you must make her jealous of the other women in your life. Don't be entirely at her beck and call — keep dating other women. Let her know this, especially if the women you are dating are the sort she doesn't get along with. She will wonder why you'd rather be with them than with her. Of course, don't take it too far: She has to know that there is still a chance of something happening between the two of you. The aim is to get her to compete for your attention — not her boyfriend's.
Use Her Friends
It is sometimes possible to attack on two fronts and get her friends to help you with your dirty work. However, there is always the risk that someone will figure out what you are up to. Aim for them to think favorably of you. If they also don't like him, they might start to ask her why she's with "that loser" when she could have you instead.
Your absolute last resort — and the lowest thing you can do — is to spread rumors about him. If you are caught doing this, you will watch all your hard work fall apart as she runs back to him. But rumors can be devastatingly effective. A whisper campaign about loyalty and commitment will create distrust and arguments in the strongest of relationships. Strengthen this by tailoring it to the circumstances and basing it on a specific issue or person that is causing problems. It is best if you can distance yourself from the rumor. Drop hints around known gossips, then wait for them to put the pieces together and start whispering about it.