Should I skip the party?

Ok I guess I’ll start by saying I’m sorry if this is long. My fiancée and I live together in his mom and stepdads townhouse. They have one side and we rent the other off them. Well about a week or so ago his mom decided she wanted to have a small Halloween party. I took the day off work just so I could come. I had a feeling that I wouldn’t have fun because I’m a very quiet and socially anxious person but I sucked it up for my fiancée. Not a lot of people came but I’d say about 10 people came. One woman who is best friends with his mom came and I honestly am not a huge fan of her. She is very rude and snobby. Anyway, the whole night was horrible. His mom got drunk super fast. She kept screaming and acting crazy. Every time I tried to talk or join a conversation I would get talked over or ignored. People just seemed to forget about me being there so I decided I wanted to leave. I didn’t because my fiancé wanted me to stay. A little while into the party everyone sat at a bone fire but most everyone went inside because they got cold. It was just me my fiancé and the woman I’m not a fan of and her husband outside. She starts talking to me about school and I explain how I’m a little behind because I had dropped some classes. Well apparently she thought she could sit there and just go on about how I need to do better and “your generation is so lazy and think they can work these dead end jobs. I went to college and look at me I never have to worry about money.” She literally went on forever and I don’t know what came over me but I just started crying. I was super embarrassed and angry at this point so I went inside my part of the house. Now his mother is wanting to have a Christmas party soon. I honestly do not want to go through that again and don’t want to take off work for it either. My fiancée isn’t angry that I don’t want to go he just wants me to be there. I don’t know if I’m over reacting or what but I literally feel so bad about all this mess.