Is it normal that I get mad at my girlfriend for drinking?

You are her boyfriend, not the boss of her and drinking with her friends at their house is not your concern. Be a designated driver for her, but lose the control-freakery.

, if you keep bitching about little stuff like this she will eventually feel like she cannot do anything and she is losing her freedom, this is deadly for any relationship. why don't you go out drinking together sometime with some of your common friends, you can see her in action and relate a bit better.

Also, if you you keep this up at one point she will start sneaking around if she really feels like drinking, and thats an even worse situation!

Not normal. You're her boyfriend, not her father. And big deal if she drinks with her friends, plenty of people do. If you don't trust her, that's your own problem for *you* to work out, not burden her with.

i talked to her about it and she said its up to me to go through that stress or not and also told me i have nothing to worry about. 

100%, and your instinct tells you she will. And it's something you have a problem with her doing, so you should probably end it.When you get drunk and you're surrounded by peer pressure, it is a fact you do things you wouldn't normally do. Why should cheating be any different? Your inhibitions are lowered anyway. If I was you I'd just end it.

OH DEAR !!! SOME ONE ENTER MY HEAD AND TAKE OUT THIS CONTROL FREAKERY....

I CAN ENd IT, BUT THAT WOULD MEAN I AM DETACEHD FROM HER. AND YEAH I KNOW WHAT HAPPENS WHEN I GET DETACEHD. I FORGET TO GIVE A SINGLE FUCK ABOUT ANYTHING.

BUT I AM NOT COMFORTABLE...

I AM JUST NOT...SHOULD HAVE TALKED TO ME. SHOULD HAVE TOLD ME BEFORE DOING IT. AND YOU SHOULDNT REPEAT ON AND ON AND ON>..THAT IT IS YOUR LIFE AND ITS YOUR CHOICE..

I KNOW THAT VERY WELL...