This is something women are socialized to do, which is to let their self worth depend on whether everyone is nice to them, and feel like a failure if they can’t manage other people’s emotions.
Your trainer is showing her true colors as a toxic controlling bitch who is lashing out at you for moving on with your life. She is showing you who she really is.
You cannot change her and you did nothing wrong in this whole process. The only mistake you made was getting involved with her in the first place, and you csn only see this in hindsight.
Nasty people can hurt you. It’s ok to feel shitty, in the sense of hurt and attacked.
But you should not feel like a shitty person or the worst person ever. You have done nothing wrong. There was nothing you could have done to make her happy.
Every time she does this it is further proof of who she is.
Being around toxic and aggressive people is draining and unpleasant. Since you now know she is going to harass and bully you every chance she gets it makes sense to change your schedule so your barn time does not overlap with her time.
I have personally found that snapping back something blunt and hurtful sets most verbal bullies back on their heels, but I am not emotionally vulnerable to any of the barn bullies I have met. It doesn’t work if they actually hurt you.
Also wearing earbuds with music around her is an idea. Just don’t listen dont pay attention.
You can’t talk this out with her. She’s a barn bitch of some variety, showing narcisstic tendencies perhaps, and you are not responsible for her behavior. You cannot change it, she will savage you if you try (only possible situation would be with a mediator that could shut her down, and it’s not that kind of situation).
You cannot change her. You have no responsibility to change her. Your only responsibility is to protect yourself.
You really do need to let go of the idea that her approval matters to you or that you can gain her approval. You cannot.
Just be very very happy you are moving, and that she isn’t your boss at work or your mother. In the largest picture this is a fairly trivial relationship and you will be gone soon. Just protect yourself as best you csn.