if they are so stupid enough to act so foolishly then, all you could do is that, ask them for proof, second of all face them yourself, as in like you only, yeah i know, sounded suicide to approach them yourself, but in which is a good way to approach them, cause you show them that you are there to discuss and solve the problem, not using violence as solution with big group of ppl, and on top of that, you know where they stay at, right!!!, if they do acted violently on you and your gf the best choice is to launch a report on them...for that im sure, they will not do anything again, even they will think of revenging or whatsoever...
well, dude go and talk to them, ask them whats the problem, solve it out like a man not like bunch of high school kids....still want to use violence to solve problems.... <!--emo&;)--><img src='style_emoticons/default/wink.gif' border='0' style='vertical-align:middle'
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violence will do both parties no good remember that, and also it will jeopardize your relationship with your gf too...and i do hope everything will be alright, sorry for not being helpful..