Looking for some guidance on what to do

I know this is very long, and I'm sorry for that, but if you wouldn't mind reading it, I could really use some help.

I am going into my senior year of high school. I don't have very many friends, just two other girls, let's call them Mary and Ava, who are my age. We all do choir, show choir, band, etc. Mary and Ava have another friend, let's call her Ruth, who absolutely hates me. She never gives a real reason why, just says it's because I'm "annoying".

Last year at Homecoming, when I got there, Ruth was in a VERY bad mood. Like, pouting at the tables not even touching the dance floor. I asked Mary and Ava who were sitting with her if they wanted to dance, and they agreed, and Ruth came too because she didn't want to sit alone, which is fine.

But we weren't on the floor for more than five minutes before Ruth started complaining, and then she blew up at me. She called me the b-word and screamed about how we were not friends and stormed off. The others followed her and they all left the dance within a half hour of me getting there, so I was all alone.

After that happened I talked to Mary and Ava about it and how it really hurt me, and so I said we should make prom plans, the three of us, and they agreed.

So last spring, I found out that Mary and Ava were planning on going to prom with Ruth and a few others for plans that Ruth made, and it was clear I wasn't going to be invited.

So I told Mary and Ava how upset it made me privately and they both claimed that I never discussed prom plans and that they were going to hang out with me at the dance, but I wouldn't have been there for dinner or pre-prom plans.

This was not the first incident like this, and so I told them I wasn't going to be their friend anymore and cut them all off.

A few months later I apologized to Mary because I was super lonely and missed my friends, and she went back to acting like nothing happened.

So a few days ago, Ava texts me about how confused she is that we never discussed the situation before and were just ignoring it, so we called and talked.

She told me that it would take time for her to build trust in me again that I wouldn't have another "episode" with her and Mary, and told me about how Ruth has a very hard home life and so her and Mary were not going to stand up for me when Ruth is being mean.

She said that it's the Christian thing to do, for her and Mary to not get involved and just show Ruth love. I am a Christian too, but I would say I'm not as well versed as they would be. Mary is very religious and Ava's father is a pastor.

I guess I don't get it, because if one of my friends was treating someone as bad as Ruth treats me, I would never stay friends with them.

Im supposed to meet Mary and Ava for coffee to talk about all this. Ive had some people say I should just let Ruth be mean to me, because it's only another year, but a lot of people also say I should cut all of them off.

I'm also scared to cut them off because they are my only friends and I was really lonely when I cut them off before.

Does anyone have any advice on what I should do in this situation?