Bridesmaid fallout / advice

Hi,
I need some advice. I’ve been friends with someone for just over 5 years. We weren’t immediately the best of friends but we were part of a friendship group, and at the beginning I would even say she would bully me or belittle me but in a jokey way.
We have had some good memories, but upon recent looking back, I have found multiple incidents where I had messaged my partner saying how she had upset me, or been rude to me when going out and how upset I was. A few weeks before my hen do she got frustrated with me and started shouting at me for forgiving my sister in law ( my sister in law cheated on my brother but they have worked it out and are now back together) I understand that she may not understand but she was angry at me telling me I was stupid and that I was a people pleaser and that’s why I forgave her. On my Hen Do she was incredibly rude to me sister in law, sneering and pulling faces at her as well as being rude towards her in comments. She also ruined the rest of the hen do by being rude to other people there cali g them selfish and being nasty. She spent the whole time being miserable. She completely tainted my Hen do and I have spent the last few eeeks crying my eyes out because of what she has done and how she made me feel. She has not apologised for any of it, and in the past she has never apologised for things she has done.
She is supposed to be my bridesmaid but I do not feel comfortable with her being there the morning of the wedding with my sister in law and other friends. I am happy to still ask her to come as a guest but I am not sure how she will respond. I don’t want to loose the other two friends in the friendship group but accept that this may be hard as they also have loyalties to her but I just don’t think I can deal with this waying over me anymore, it is ruining all thoughts of my wedding and planning.
I am not one to stand up for myself which makes things really difficult. I am completely afraid of her as well ….. I feel unable to say it in person due to her response and how she will treat me - I’ve discussed with my family and partner and have agreed to write it in a letter. Does this seem acceptable?
Any advice or anyone been in similar situations happy to share their experiences ?