Is it normal to fuck a girl who has a boyfriend

Might end up being a little long, so have patience.

Ok so there's this girl I work with who is a year younger than me and really hot. I started talking to her a few months ago, and we got to know each other pretty well. Then I found out she has a boyfriend.

I still kept getting to know her and I still flirted a little. She had a dream about me, in which we layed in the same bed and I comforted her.

The next day I went to a party and she was there with her boyfriend while I was there with my group of buddies. The party got busted around 11:30 so we headed out but eventually met back up with her and her boyfriend. We got drunk and smoked a few bowls at a local park. I was talking to her boyfriend and realized he's a pretty nice guy after all.

Then, in the back seat of the car it was her in the middle, me on the left and him on the right. He had his arm around her but her hand reached for mine and we ended up holding hands for the whole car ride home without her boyfriend seeing.

That night, I had a dream about me and her having sex. I even told her about it and she didn't seem to care. We talked about how we managed to hide holding hands from her boyfriend and she says "I don't regret anything".

The following night, I go to another party and get pretty crunk. I phone her and we talk on the phone for about half an hour. Don't really remember the conversation, but from what she told me it was really flirty.

She was sick the next day so I came to see her, and we watched a few hours of the OC together cuddling. She dropped a few sexual jokes, basically saying she would have sex with me. I almost made a move but she was sick so thought I'd wait.

Our personalities really match up well and we know each other so well already. She even dedicated a love song to me and she says I love you a lot, not as a friend would say it.

Should I give the relationship a shot? Or should I tell her I won't do anything with her unless/until she breaks up with her boyfriend? Is she playing me or does she seem genuinly interested in me?

Also...is it normal to fuck a guys girlfriend without asking any questions?