I agree with AnnabelMore. I don't think your feelings are inherently wrong, people can grow apart, it happens. I do think though that it's been handled badly.
And I think regardless of what happens with this particular relationship, you need to work on communication. You seem to have issues with confrontation, and the problem with that is that other people aren't mind readers. It's good you told your wife how you felt. But you should have told the GF, as well, as soon as there was an issue, and worked through it together.
I don't know if anything is salvageable now, but I'm pretty sure things could have been worked out at the time. Maybe you would have drifted apart, but she would have been made aware of it, so instead of holding tighter, she would have looked for other things to hang on to. It would have been easier for her, and for you guys.
So I'm not saying you're not allowed to break up with her, but please be aware that you are partially responsible for the amount of frustration you've been experiencing. You allowed it to build up until it wasn't sustainable, instead of talking about it from the start and through the whole thing.
I'm well aware that even little things can become frustrating and anger you when things have been going on for a while and haven't been getting better. But while it makes sense to be upset if you have been asking her to go every time and she had insisted to stay every time, the anger you have for her not leaving when she doesn't know you would prefer her to is in my opinion, mistargeted, and you should take responsibility for letting it happen and hoping other people would change (why would they, for no reason?) rather than asking them to.
I realise that right now you're angry, resentful, and probably likely to lash out a bit at her, but I would suggest you be as diplomatic as you can. And diplomatic doesn't mean you can't be firm. It doesn't mean saying things you don't mean, like offering something and hoping she'll decline. It means saying "I want more time alone with my wife" instead of "get out!"