Kate. Thank you! I feel that I didn't explore enough options; yet, there were no options to my knowledge to explore. It happened so quickly that I end up asking myself "If I made a hasty decision" but then remind myself that a professional (Ella's Vet) was right there and in his opinion, this was the only option. Nonetheless, I love Ella and miss her. I have kept her collar and will be framing it in a shadow box and will put it on the wall. Thanks. I really appreciate your detailed answer. It helps to hear from a professional.
One last question. "Did I really do everything possible?" I didn't try behavorial training or anxiety medicine. Vet did not seem to think that this would have helped. "Did I really do everything possible?"