My boyfriend and I are together for 3 years and both in our mid 20's.

Two years into the relationship he met this girl from work and they quickly became friends. I never really liked her, she gave me nasty faces and all. Clingy behavior. My boyfriend said this was all in my head.

Now they are quite close friends. This girl has won a 3day trip holiday to another country. Since she calls my boyfriend "her best friend" she asked my boyfriend to join. I do not want this. Although he says he can fix different hotel rooms, the anxiety that this gives me is insane. 

If he would go, it would be an almost free holiday for him. He is angry at me because I don't want him to go. He is still doubting.

I cannot join, since I have to work and I don't even have money for my own tickets and all that.

Am I an asshole for refusing this to happen?