Well this is tricky... my fiancé is bi and was recently in a two-year relationship with her ex girlfriend. She cheated on her a few times with me before they broke up and we got together immediately afterwards. She has told her ex that she still misses her and I have found out but she just tells me "she was my best friend". Now I find her texting her, calling her cute and when I ask about it, she replies "I'm only being friendly". I told her it was either her or me, so she stopped talking to her. A few months later, I look on her phone and find her still talking to her and she even stalks her Facebook page and I ask her abou it and she denies it all. I need help. What do I do? :/

Seriously? You're engaged to this woman knowing what you already know about her? This sounds like the moment when an ultimatum is required, but honestly, you've already done that. You told her she needed to quit contacting her ex, and she made excuses to continue. Sure, the "BFF" argument is tempting, but if my ex-lover of either sex was also my best friend outside my current relationship, I'd expect my fiancé to be more than a little concerned.

If all is truly on the up-and-up between these two women who are "just friends", then you should all be able to comfortably socialize together. Try asking for that. If the answer is a resounding "NO WAY!", then I'd say you have your answer. The difficulty in bi relationships is that it's too easy for the current partner to overlook a connection to another partner of the opposite sex. They were already lovers, she already cheated WITH you. There's nothing to suggest that she won't cheat ON you if you don't take the reins here and bring the situation out into the daylight. A nice dinner out for the three of you (or four, if the ex also has a new partner), would give you a much better insight into what's going on.

If I try to bring this up, she will leave me. She never tries to work things out with me, she just threatens to leave until I forget about the conflict. I love her so much and it's so difficult... I don't want to lose her, but, I also don't like being lied to.

Bi or not anytime your in a relationship with someone else being close to you ex is a no no. Being cordial with your ex is one thing but
Facebook stalking them and chatting with them constantly is
Something entirely different.It all boils down to if she truly cares
She will do what is best for her relationship.

Vissik, what kind of life are you envisioning with a woman who wants to be free to do as she pleases and won't sit down with you to discuss your reasonable concerns? I'd be more worried that she won't leave than that she will! I foresee a great deal of upheaval and pain over the years if you continue to allow her to control the relationship through fear that she'll leave. That's not a mature and sensible behavior pattern.