I (22F) no longer want to be friends with my former best friend(20F). She's getting married next year and I am one of her bridesmaids. What is the healthiest way to go about ending the relationship?

I became friends with her through work about 2 years ago, and we grew very close. However our relationship has been rocky since a fight we had 6 months ago. Ever since then I have been evaluating our relationship as friends and her as a person. I've given it plenty of thought and I no longer want to be her friend given her action and behavior. The main reason is I feel I can't trust her, but I also feel like she isn't supportive enough in the friendship and I need. She's nice and friendly towards me always, but when things get serious I don't feel I can rely on her. She's very flaky and unreliable, and I want a friend who is dependable and isn't only my friend when its convenient for them. So I have unfortunately decided I no longer want to be her friend. Currently I am slowly distancing myself from her, as I thought it would be the easiest way to end the relationship, especially since we work together and I see her quite a bit. However, she is getting married and I agreed to be her bridesmaid a while ago. I do not want to be her bridesmaid anymore, and I honestly don't even want to go to the wedding. What is the kindest way to go about telling her this?
TLDR; I no longer want to be friends with my former best friend, how do I tell her I don't want to be her bridesmaid anymore?


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