I've been going out with my girlfriend for a year and a few months ago she met a guy online who lives 500 miles away and suppossedly has a girlfriend. Everything was still great until she thought that I stole her password account to Facebook. So she decided to have him post loveletters on her wall to get back at me making me think that she was going to move there and live with him. I immediately lost all trust and wanted her to stop being his friend but she wouldn't have it so I had to deal with it and try to have her regain my trust. A couple months passed and everything was fine even though she was playing fake poker with the guy until the early morning hours and talking to him via webcam until 3 am in the morning. A couple weeks ago she decided to give him her phone number cause she was bored of poker. Now she is talking and texting this guy about 5 times a day at a half hour at a time at all hours of the day. I'm starting to feel threatened by this guy again because of how many times a day they talk and she's telling me that she's just having intelligent conversations with him.
I'm ready to give her an ultimatum and tell her to choose between me or him. I love this woman so much but I feel threatened by this guy. Should I trust her? Am I just being insecure? Please help!!

Ultimatums are never the answer to fixing a relationship. Now to the question of feeling threatened, its way beyond that, you should be feeling USED. She is not even into the relationship anymore, if you haven't noticed, she has moved on and is basically in a new relationship with this guy.
Just because he is 500miles away doesn't mean a thing, she is emotionally connected to him, NOT you. The reason she is still has you around is because this other guy is 500 miles away, and she needs you as the fall back boyfriend.

Its time to move on and stop being with someone who has so little respect for you, that she plays games with your feelings with some other guy by posting love letters on the computer for all to see. Get out and find someone who will appreciate having you by their side and not be looking somewhere else for love.

Should you trust her? That is up to you, only you know her and yourself and no matter what you might get as a answer here it really boils down to "Can You?" because if you can't or don't think you can then this relationship is over, relationships without trust are ticking time bombs that WILL end, maybe now, maybe later. Are you being insecure? Yes, you are being insecure, you should be able to control your emotions and not feel anything by a guy that is 500 miles away, but no one is perfect :) . Now man, do you really want to be with a female that is playing with you, it seems to be as if you are telling us things that she did to make you jealous or punish you for possibly stealing a password to her Facebook account? That is wrong man, I don't know how old you guys are but these are very immature games to be playing, so yeah give her the ultimatum, if she stops then congratulations, if she doesn't, then move on to the next thing. Just keep one thing in mind, if you do an ultimatum and she doesn't "cooperate", then you immediately LEAVE! So be ready to do that if you are planing on feeding her one.

Good Luck,

Javi

How do you know she is online all the time? How old are you? Sounds like juvenile games to me, and instead of games, and ultimatums, get a new girl who doesn't feed your fears, and insecurities.