10 Points!! How do you confront a bf/gf who you find out has been having a year long internet Fling?

Last night, my longtime girlfriend of 5 years, .. Fell asleep around 8pm with her computer on. I took her computer to check my email real fast. Because I left my Laptop at work. Then, some man sent her computer a message saying " hey girl". I Went into the Yahoo Archives Box and discovered the history of transcripts , she had been having nightly conversations with this guy, about every night.. And these conversations would sometimes last 5 or 6 hours. Literally. I was really hurt, but what hurt me the most was reading about how she painted our relationship to this guy. She frequently told him that I Leave her alone by herself all of the time, and that I work from sun up to sun down. Told him I hang out with my friends with my free time everynight!!!!!!! Which is a Lie, I hardly ever see my friends anymore. I read maybe 7 or 8 conversations, often he would ask her what she was wearing, and she would say she's sitting by the pool in a bikini or some bogus stuff " Nightie"...My girlfriend is white, And I'm bi Racial blk/wht... My Girlfriend and i have 2 children together. So Technically they are 1/4 black. I read where this guy was saying stuff to my girlfriend, making racist comments about me. Saying she should take me to the hospital to get checked For AIDS because " Most blacks have diseases". This guy told her almost everynight that she needed to leave me, and be with a white guy. When my girlfriend got pregnant, I told her to quit her job, ( Waitress) And I moved her into my house... I have been taking care of her ever since... Brought her a New car last year, Cover all the bills and the Rent..Built a Pool outside for her and the kids... I work my @SS off to provide for her...She has a good life, And our relationship has been going great... I was really heart broken... When I Confronted her about it,I told her I was really upset about was how those racist comments he made towards me, in an indirect way, were also racist against our son and daughter aged 2 and 4. She told me she thought he was " Kidding " Because he loved to make jokes. Then she went off on me and started screaming at me about how this was my fault, and if I gave her More time, she would not have done this. She said this was a Result of Me Not Spending enough time with her. She also says this is not cheating. The weird thing about all of this is, my girlfriend has told me so many times, over the last 5 years, that if she ever found out about me seeing someone else, she would take the kids and never speak to me again. I'm sitting here at my office, I'm so upset about all this ... She didn't even come across as if she was sorry. In a way she seemed proud of her actions. What should my next move be? I' dont know if I could get over the fact that she was devoting so much of her time, to a very racist man. Does that mean that she herself might be slightly racist? She never defended me when he would make these comments. I'm really lost.