<human>: I got out of a one-year relationship in May, i met this girl at a party a month ago. 

We opened up and told each other we liked each other. I still wasnt over my last relationship and she knew it. I would hate putting her in that position, knowing full well that i was only using her to replace who i just went out with. I didn't want to hurt this girl, i liked her.

We talked it over a lot, and i told her I would go out with her, but only, and only, if she was fully aware that i'd just be using her to get over my ex and that I had that corresponding emotional baggage. We explicitly and mutually agreed it wasnt just friends with benefits. 

She was cool with it. We slept together, we hung out in the city on a weekly basis. it was a dumbed down relationship but i never had a problem with it. At times it felt more like FWB but we always called it a relationship.

She slept with someone else four weeks in. Crazy thing is, i dont really feel bad about it. Sure, i feel shitty, but i dont really feel... that bad. I was using her, we both knew it. 

My questions here are: do i even really have reason to feel bad? It was a fucked up relationship, for sure, but did she have reason to cheat on me? Was it justified in the context of the relationship?

I say no, but given the strange nature of the whole thing, i'm not sure if im reacting appropriately or if she was acting inappropriately. I'm just confused and want a second opinion on the whole situation.

I'm not even sure if I shouldve done the whole thing in the first place. I'm wondering if it was fucked up of me to do it. I never had bad intentions, and made sure she knew what she was getting into, but that fact notwithstanding, i wonder if I was out of line. Again, a second opinion would be awesome right now.

Give me the gist of the text in a nutshell
<bot>: entered a relationship* with a girl, she cheated on me a few weeks into it. I don't even feel bad. Am i reacting appropriately, was she out of line? Did i fuck up in going out with her?