I feel for you, and I had the same sort of situation with my mare. Hindsight is 20/20 and now I get where I went wrong and I will never make that mistake again.
Picture yourself, and one day a different species comes to your home, takes you away from your family, your life, and everything you know, and puts you in a different house. Would you be calm and happy? No, you'd probably be distressed, upset, mad, scared, and a nervous wreck.
Some horses can take changes better than others, just like us, some people embrace change and some fight it every bit of the way.
I would say hold off on the trainer right now. Let the horse do their own thing, start new relationships, get used to her new surroundings. Let her bond with you before trying to tie her up, because she doesn't trust you right now. Let the bonding happen, don't be in a hurry, it can take months. Let her come to you, take baby steps. Treats should not always be used as bribery, but you can start out with them by just getting her attention and rub/scratch her (do not pat) briefly, then walk away. Leave her wanting more positive attention.
People can fall "in love" with a horse instantly, but we do not realize that they probably do not feel the same way. Let her bond with you first before asking her to trust you, and take it in very small steps over weeks. Just halter her and let her on a lose lead rope, don't tie her. Rub her down, scratch her, breath in her nose (if she lets you do this, and she blows back this is a huge compliment). Let her smell you all over if she likes.
Spend time with her every day, even if it's just cleaning out her stall, feeding, hanging out in her area. Once she has started trusting and bonding with you, then it will be time to try working with her.
You will know it when it happens, and it will be the best feeling ever!! Good luck, and don't get discouraged, just take it slow and don't rush the process.