I think the “I’ve never fit in but want to be accepted” is your answer. What if this is her way of bringing you into the fold in a mostly relaxed and fun setting
Don’t force yourself to go if you’re going to feel uncomfortable, but also, you are allowed to have fun after what’s happened to you. Please don’t feel guilty, it’s not your fault. Have you considered therapy?
If you don't want to go, then don't go. My SIL invited me to hers last year, I politely declined, not because I don't like her, but because it wasn't my thing (she knew it wasn't anyway)
If you don’t want to go don’t go Imagine bringing negative energy to an event you already don’t want to go to and dampening the vibes for everyone else When you could’ve had a pleasant weekend without them