I'm so sorry. How awful for both of you. I had the same doubts when I sent Loca to the bridge this past June; in fact I cried after having read your post. It's a horrible feeling, but as things start to settle down and you can view the situation more clearly, you'll realize that you spared Layla from having to live in pain.
Please be kind to yourself. You did the right thing and you made your decision out of love after having considered the options.