I want to work past this and trust people to be my friends again and I don’t know how.
I write a letter (not to be sent) to the friend and say all things that could not be said and were not said. Although it may start with anger, I also add why I appreciated the friendship and why I missed them (and in the end, why things will have to be the way they are now).
I also write a letter to myself. I apologize to myself: Did I let myself get treated a certain way? Did I behave in the best way? If not, how can I behave differently in the future? (The part that may help you here, OP, is that I include things that may have been warning signs/things that I may not let happen in the future/and how I will try to treat people more compassionately in the future (so I don’t do what I experienced to someone else if I was on the receiving end, or if I could have behaved in a different way, I write that out).
I continue writing both parts until I feel at peace (peace = not being grar grar with the person, peace= I think that I learned what I need to so that it won’t be an infinite loop in my head).
Write an action plan. If you lost a friend who used to do X with you, what is your need now? More friends? Different type of friends? Where will you meet these friends? So I usually wrote out a list of activities, things that I wanted to do with fictional new friend. In an odd way, this last step has always worked for me. A few months later I meet a person who fills that niche. With time, the pain from the other person is gone because you have other friends and activities that fill up your world.
So for your need to learn to trust, part of what you could focus on if you do the writing exercise is include 1) any warning signs that you think you saw 2) in your letter to yourself, how you won’t do X (if that is important to you).
When writing your action plan and later carry parts of it out, remember that people are individuals. If person X did something, the likelihood of new friend A, B, and C doing it is phenomenally small.
Last bit. A very good friend of mine uses this analogy for friends. Think of it like trains going different directions.Maybe you will ride along on a train with someone for a while. Then they will get off and go on a different train to a different destination. New people get on and you may ride with some of them for a while. You may ride with a few people forever. But they are all going to their own destinations. Just enjoy them while they are on the ride with you in the same compartment.