Barn drama is good practice for all kinds if drama later in life... work drama, in law drama, barn drama (lol).
You can't control drama and gossip. You can only control your response to it. People believe what they want to believe.
I would speculate and imagine that there is a lot of jealousy at your old barn about your current horse situation. You've gone from being an absolute beginner with no knowledge, grateful to ride any horse at all, thinking your trainer was an expert, to the owner of two beautiful horses with growing knowledge, skill and experience of your own. You've seen what's "behind the curtain" of your old trainer's skill and knowledge, and it doesn't seem like you worship her in the manner she expects. When I read your posts, it seems as if you've probably surpassed her in most areas of horsemanship and ownership. You've bypassed her and found a new mentor to help you with your horsemanship.
I enjoyed lessoning and leasing at my old barn. I have some horse friends from that barn that I enjoy running into at events out and about. I appreciate the knowledge and skills I built there, and I appreciate that my old trainer helped me find some of our horses. I left amicably, and would never badmouth her in public. I will admit that towards the end, I, too, was beginning to "see behind her curtain," and some of the things she said and did regarding horses were not congruent with my values. Once I had my own horses (Salty), she promised to help me, but never did. She gave me some bad advice, and Salty wouldn't be around if I'd followed it.
This sounds boastful, but over the last year, I've become an expert on my own horses. I'm constantly acquiring new knowledge and skills. I've found some great new mentors. I read, I research, I ride, I attend clinics and events, I spend hours with my horses. I really see her more as an equal, now, instead of an expert or mentor.
You are not going to have the same relationship with your old trainer because she doesn't want an equal friendship. She wants to be the expert who owns and controls the knowledge and horses, and you are supposed to be the kid who is unquestioning and ever-grateful. You can't win this one because you've moved past her.
Go tomorrow. Smile, be courteous and kind. Be full of grace and rise above the petty drama. Find a quiet moment at the end of the day to say goodbye to Justice and thank him for his contribution to your journey. Thank your old trainer, turn and walk away with your head held high and a smile on your face, and be done. Cry in the car if you need to.
You have finished that chapter. Turn the page. You are creating your own story and have new things that require your time and attention. Don't look back, keep moving forward.