First of all, sorry that you had an awful time and people were horrid to you.
However, it sounds as if you are one of those lovely people who give in for the sake of others and don't put yourself first.
Anyone that lays a guilt trip on you, and knows how you feel about the other people, is also bullying you by cajoling you into going.
If you were my friend and I knew you would feel uncomfortable I wouldn't want you to come just for my sake. I'd suggest that me and you go out on another night, together or with other people who are all friendly with you.
Ok, we all have to do things we really don't want to do sometimes, but I get the feeling that you often do stuff you don't want to do and as a result often get picked on because of your affable nature.
Tell her no, you are not going and wish her a great time but say you will meet up on another day and go out for a drink/meal etc.
I would hate, absolutely hate for one of my friends to be put in the position you are in.
Anyway, if you really feel you want to go, well go and buy something fabulous and rise above the horrible people as nice people radiate an inner beauty that those horrible people will never have.
So what kind of budget do you have, my lovely?