Did I Totally Over React and Manipulate Things?

My gf unavoidably has to spend a lot of time within close proximity to a guy whom I have issues with and don't like her being near. I do nag at her a bit about it and she got a bit annoyed and I apologised and agreed to trust her. Anyhow the next day she had a freshers event (she's a rep) anyhow she invited me along, and the atmoshpere was good and everyone was quite drunk anyhow, we were both crossing the dancefloor when she saw another of the reps and gave his bum a quick feel right in front of me. He gave her no encouragement whatsoever. I naturally was furious and went mad at my girlfriend , I know she wasn't cheating or anything but I just thought it was horribly disrespectful, and I would never dream of doing that to another girl. Anyhow I told her i felt like a complete fool and she's making me look like a guy wih a giflfriend who acts up for it and tarty even when im around. Im finding it hard to trust her now if thats the kind of thing she does whilst im around.

We subsequently went home and i wouldn't kiss or touch or hug her, then I walked out of the house with her pleading and crying and ignored all her phonecalls and texts for hours until replying with ominous messages about just seeing her when I see her. All the time in the back of my mind I knew I wouldn't break up with her, but I found myself actively making out like I was going to. I don't set out to be manipulative but I find myself doing things like this regularly to get the upper hand. Am I being out of order and did I over react about the whole thing? Or did she disrespect me as badly as i thought?

I think you over reacted quite a bit. Pinching someone's bum isn't exactly a big deal. Of course, you'd be annoyed, but surely you could have just said "I don't really like you doing that", rather than basically calling her a tart?

The thing I have the most issue is you trying to manipulate her. Alright, you were upset, but stringing her along was malicious. You could have just told her that you were upset and didn't want to talk to her for a while. Basically, I think that you have the right to be a bit peeved at her (although personally I don't see the big deal), but it was totally OTT to walk out, ignore her completely and leave her crying and worrying that you were going to dump her. If you do things like this regularly to get the upper hand, then that is actually not far short of abusive. I'd dump you for it.

I know it was a one of and she wouldn't usually do it, but it makes me so angry that she has the capacity to do that and I would never ever dream of doing, let alone in front of her. Im not possesive but it makes me feel sick to think she could be doing that to other guys. She's not a cow and it was totally out of character and I felt hurt because we both agreed the limits within our relationship. For example earlier in the evening i was talking to another of the reps (girl) whilst she was in the toilet, shes insanely jealous of this girl and thinks shes after me, anyhow I was just talking to her and she like storms out and totally cuts the girl off like theres something going on, then she does something like that. I'll never be comfortable with my girlfriend being like that with other guys it may make me uptight or whatever but I just don't like it. I really don't try to manipulate things but I feel like im making her think that I care less than I do and that Im the one who could more easily walk away from the whole thing, so she feels worried about losing me, it makes me feel uneasy afterwards.

The point is my girlfriend would go crazy i I pinched someone else's arse so yes it is a big deal.