I know it seems like a big deal now, but trust me...this too shall pass.
You have a few choices. First, you can "get sick" at the last minute, claiming that you don't feel well enough to go. Sit this one out...no one will care and if they do, they'll forget about it by Monday morning.
Second, you can just watch the stinking movie. If you don't like it, you don't like it. If you're the minority and everyone else wants to watch them, you just have to go along.
Third, you can more forcefully suggest doing something else. Bring along your own movie...maybe even get something that's suspenseful or scary, but at YOUR level of tolerance.
If the party hostess is your best friend, just take her aside and tell her they keep you up all night and you hate them (or whatever your actual problem is with them). If you're good friends she should understand. If she doesn't, just let her be mad...she'll get over it.