DITCH HER!! Trust me, we are not all like that.
Your mates, as been said above, probably can see what she is doing to you. Get rid of her and get your mates back. For satisfaction of other needs there is always your right hand to get you through the dry spell until you meet someone who is worth spending time with. Sorry to be so blunt but it is true.
There are also a few lovely ladies I could introduce you to if you are in the Midlands
Trace
Oh, I just noticed, you are!