A group of friends convince Another ‘sort of’ friend who is female to attend an underground rave. She gets separated from them And is scared by people wearing ?Animal masks? There are tunnels. She decides to fight back with whatever was handy ?An axe? After she kills a few people the friends tried to tell her it is just a joke. She then kills them anyway because she is different somehow or just scared.
I saw this movie maybe 5 years ago. In color. It is in English And some other language possibly. Maybe she was visiting a foreign country. The prominent animal mask was a ram maybe.