My dog just passed and I feel broken

I know that this is probably a very common post here but my dog just died this night and I feel destroyed. She was a 11 years old German shepherd indoor and outdoor, living her best life. An old owner didn’t like her and so he just gave her away when she was 4 months old, I took her when I was in a depressive state of my life. She started feeling sick and degenerated very quickly (24/36 hours) until we had to put her down. The vet said that it was multiple things (inf3ction of the uterus, breast cAncer and also an intestinal occlusion); l've almost completed my medical degree so I feel like this emergency could have been treated differently (or at least I would have), however I don't want to overthink this, now that is all over. I feel a sense of guilt because maybe I could have changed the clinic (I thought about it but I preferred to not stress her more) and in the last few weeks I didn't give her the usual attentions because I was always focusing on my studies. I hope l've been a good friend for her and that one day she can forgive me for these last moments and if I made a mistake in the choices of her treatment, she has always been loyal to me and she always loved with all she had. I'm new to this community so I'm sorry if this post is off topic but I'm broken and I needed to write that down. Thanks everyone, and thanks to my dog, Ariel.