(((beccaB))) I'm so sorry for you loss. I'd weigh whether filing a complaint will make you feel better, or just draw out your grief, before going through with it. You tried your best to get her help. You may have been able to prolong her life a little, but it sounds like she was in a bad place.
I went through a long, drawn out, painful death of a cat, and a short and sudden one, and in both cases, I felt a lot of guilt that I didn't do the right thing, that if I had done something different, they wouldn't have died. In hindsight, I know I did my best for them. So did you. I hope you can find comfort in that.
'02 Eddy Merckx Fuga, Selle An Atomica
'85 Eddy Merckx Professional, Selle An Atomica
'10 Soma Double Cross DC, Selle An Atomica
Slacker on wheels.