throwthebook - Your 'friend' has been the architect of his own misfortune.
Drunk, or not, glassing someone because he has got his paws on a girl you have decided belongs to you, is not a reasonable response.
The girl is, not unnaturally, upset with him but it is NOT her pressing charges, it is the judicial system.......because nice fella as your friend may be, he glassed someone.
It is a shame that a moment's madness has had such serious repercussions but that's they way these things go, I'm afraid.
Have a look through previous questions on this site which involve incidents of 'glassing while drunk' there are a depressing number of them.