I need some honest advice and help PLEASE! 😣

I lost my soul dog four years ago and I never properly recover. I purchased the first dog ( teacup yorkie girl) from a breeder and then lost her in 2022 and then suffered in silence ever since. Her sudden departure took some joy from my life that will never come back, and many things lost meaning since she’s gone. I’m just not the same person anymore. Considering that I had purchased her, I felt a moral obligation to adopt a dog, if ever I would want another dog. I will soon be moving to a new place where I will live alone and I started thinking that MAYBE sometime in future I would perhaps consider the idea of a new dog. Recently, I started volunteering at the shelter and I saw a dog that reminded me so much of my bestest girl and with no proper plan, I took her home to foster her(11 month newly spayed mutt). It was a week ago, and I cried every single night since because she reminded me of my dog so much. In the meantime I told the shelter I want to keep her. I am very caring and very attentive, and I kept good care of the dog that I brought home but today I had a situation at the vet that triggered me. I took my new dog to the vet to get some tests done and she went crazy, even bit me several times as I held her when they tried to take a look at her gums because she has rotten breath. She was in so much stress and fear when they tried to do a check up, she squealed badly and my hearth broke, I couldn’t take the sound and started crying. She was given a sedative to calm down so that the vet could examine her properly. I took her out until it started working but I couldn’t stop crying. It triggered me since my first dog died prematurely due to an essentially vets mistake and I felt so guilty for taking her there. Anyway since I cried so much I became numb, so numb that I feel like I don’t have any feeling left for the new dog. I don’t know what happened. Since I brought her back home I don’t feel the need to hug her like I did this week. Please, please if anyone can understand and give honest advice, I would be forever grateful. I don’t want to return the dog, I want her to have a happy life and I can’t imagine her back in the concrete box, terrified and confused. What should I do?!?!😭😭😭😭😭