I’m so sorry that happened, truly. Honestly, though, you deserved to have better medical guidance during that time and it really isn’t your fault for not knowing. I think that at that point, though, it was way more important for her to be comfortable above all else. She was lucky to have you there.
my parents and my grandma have each lost an animal due to unnecessary/overdone procedures… likely so the vet could make more money. most recently our family cat nearly died because they gave him a leukemia vaccine even though his breed is known to be allergic to leukemia vaccines and we brought it up. i wont even get my cats teeth done and ask about every shot they put in him because i am so paranoid
edit: always get second opinions and trust your gut