<human>: To keep it short, there's a girl I met online 8 or 9 months ago and we got on really well, turned into good friends (good internet friends I supoose). Talked every day, fun conversations, lots in common and lots to talk about. Just generally really liked each other as friends, wanted to meet up at some concerts.
If there was nothing stopping us I can genuinely say we'd be awesome friends right now.

In the time we spoke I gained feelings for her, more friendly than anything, just a general attachment to her I guess. I miss her when we don't speak, I love it when we do.
My girlfriend hates it and has always hated it. We argue and fall out about it often, so I can definitely say its destructive to our relationship. I love my girlfriend more than anything but I just can't seem to get this girl out of my head! 

Recently my girlfriend messaged her and basically told her she's ruining our relationship and that she should stop it (a polite fuck off to be honest). This is light compared to the last time it happened. 

Anyway the girl told me we should stop, she feels guilty for 'ruining my relationship' and I feel guilty that she has to deal with that.
We messaged once or twice more and then stopped, from normal to nothing in the space of a day.

I just don't know what to do. I love my girlfriend and would never want to lose her or replace her with some internet friend, but this other girl means a lot to me, it's like I can't just forget, no friend I've ever had has been like her, she's just perfect and I want to talk to her and meet her but I can't.
I feel so stressed because I know I only have to send that message and she'll be there, I know she would happily talk to me again but there's his invisible barrier stopping it. It feels so forced and fake but I have to listen to it.

I know you'll just tell me I need to support my girlfriend and fix things and forget this girl but I really need to talk about this...

Can you condense the text into a few key points?
<bot>: I have feelings of some kind towards another girl and a good friendship with her but it's damages my relationship with my girlfriend and she has forced me and this girl to stop talking to each other and now I miss her