Oh hon, I'm so sorry. but there isn't anything there to forgive. You gave her a long beautiful wonderful life full of joy. She knows it's time, and will welcome release. It's sad, heart wrenching and among the worst things to ever happen, but you are ensuring that she doesn't suffer at all, and that all your memories of her will be cherished. <:) Letting Coco go last year still breaks my heart, but I know it was the right thing to do. She, indeed all animals, are love. Just pure unrestrained love. For us and the world.
*all the hugs, tight to hirself*
Be strong, dear. My prayers to you for healing to come as soon as it can.