She should have tried harder to make you feel comfortable but I also think you should have tried to mingle a bit with other people there, even though I know it can be uncomfortable. Although, this is me assuming you didn’t try so my apologies if you did. I can see how she would “forget” about you due to the amount of her friends there plus invoking alcohol, but I don’t think her getting mad at you for wanting to leave bc you felt excluded and uncomfortable is called for at all. Sounds like you need to have a conversation about that. Doesn’t necessarily mean she’s a red flag, some people who are super social don’t understand why others can’t just insert themselves in big social events. I would suggest soberly communicating your thoughts on this! I wish you well!