I am so sorry for the loss of your beloved little girl. The circumstances are so sad. You did everything you knew to do, please don't blame yourself.
Grief is a very hard thing and you are going to feel this for quite a while. I lost my beautiful Ginger this summer after 15 years. It was because of something I did. I let her swim in a stagnant pond on a sandbar on the river. She took in some water as did my new pup. They both got Giardia the pup made it Ginger couldn't. I still feel horrible and miss her SOOOO very much.
I know she had a good life. Now she is in heaven with our daughter that loved her so very much too.