Nervous about a party,help!?

[Ariella]

My ex boyfriend who me and my current boyfriend are actually good friends with has invited us to his 18th birthday party this weekend. I was really excited to see people from my old school until I found out my old group of friends who fell out with me for no reason when I moved schools last year and we haven't spoken since. I feel really uncomfortable about the whole thing as I don't know how they will act towards me and how I should act towards them. I plan to speak to them when spoken to and be polite but short and act as if I don't care. However I am worried incase they act immature and either say something snide/***** to me or even do something such as "spill" a drink on me. There is one girl who is known to be quite aggressive and I wouldn't put it past her to act violently. I just feel sick even thinking about it but I've said on a Facebook event that I'm going, I don't want to miss out or disappoint my bf by not going or incase they ***** about me to him. So how should I act?!