Nervous about a party im attending?

Theres a girl from another school that likes me that invited me to her party that shes having. She said there will be about 40~60 people in her house and they arn't from my school either, which means theyll all be a complete strangers. To make things worse, this is the first party THIS BIG that I will be attending. It just a casual party with alchohol and etc. Im pretty shy when it comes to strangers when i have to talk to them, but at the same time, I don't want to seem like a loser and I don't want to make her feel like I'm not having any fun. I get a bit more loose when Im tipsy, and i might start acting crazy, but I just want to ask for some suggestions. I don't want to be just there by myself the whole time while everybody else is having a fun time. What can i do..?