To Lodje and others:
She didn't leave the chat open on purpose, she left it open because she forgot (fail). I see that you strongly support the opinion of me breaking up with her, and I would certainly do that myself if I had lots of emotional feelings for her. I would of done it now, at this second, and I'd make her cry! But that is not the case. Im into this relationship to work on my skills as a boyfriend (sexually etc) and to have a bit of fun, which I have, and there are some reasons that are keeping me from breaking up with her at this moment:
- It gives me social status to be with her, she's very pretty, and I LIKE social status
- I can find sex elsewhere, but to adjust to a new partner and be disappointed of her blow-jobs is quite stressfull, and it takes time to find a new fuck-buddy too!
- She's a cool person to be with and we have lots of fun
I have only two options in my opinion

Here they comes...
1) TELL HER THAT I CAUGHT HER CHAT-LOGS AND DUMP HER RIGHT AWAY. In one way this is nice because she's not a good girlfriend at all, but it would also give me the paranoid-boy reputation and I don't want that, lol
2) PRETEND LIKE NOTHING HAS HAPPENED. This is good because it will still give me sex and a bit of fun, but it's bad because she will most likely cheat on my in next to no time, and I don't know if my self-value would handle it.
So, if I decide to break-up with her, how to mention the chat-log without being a paranoid boy looking at her logs because I am needy and insecure?
- Consistence

You don't need to give her a reason that you are breaking up with her! Just say I don't think we should see eachother anymore and leave. Her mind will do the work for you, she will eat at herself to try and figure out what she has done wrong. If you provide her with reasons, you provide her with tools that allow her to defend herself even if only in her mind.
Example: If you tell her you read her chat she will be able to justify it in her mind "He does not trust me and is snooping around behind my back" which allowes her to see you as the one at fault and completely ignore the fact that she does not deserve to be trusted.
Example: If you just say "I don't think we should be together anymore!" she will not have anything to associate the break-up with and thus cannot pass the blame off on you in her mind. She will start to wonder why you broke up with her (i.e. another girl, bad sex, loss of attraction, being a bitch, etc...) which will self compound and grow like a cancer in her mind. It will drive her crazy for a while and most likely she will see you as more valuable because you are willing to leave her. The one who breaks it off first is always the one in control of the situation.
Peace...