Don’t beat yourself up about Delilah passing away at the vets.
Yes she wondered what was happening, but it was only for a second or two, then deep deep sleep. You did a kindness for your beloved dog.
My old pointer passed in his basket during lockdown, he had cancer, had all the drugs he needed to keep him pain free. Phone calls and videos to the vet - we worked together to give him a reasonable end of life. He passed with me at his side, BUT maybe I should have let the vet take him for the injection? I could not bear for him to be alone at that time, but did I do it for myself? Perhaps he suffered by me keeping him at home? I’ve had many dogs and still have two beloved pointers, but he was so special, the naughtiest the cleverest, one who understood what I was trying to do and we had a superb relationship, I could do anything with him, gundog work, doggy dancing, obedience, agility. Dog of a lifetime.
We do what we do, we have to make the decisions and face the consequences. It isn’t always easy.