I'm so sorry, KiChien
You know she loved you as much as you loved her, and she knows
your decision was made from love. Don't feel guilty--you did what your heart told you was best, and your heart is the best judge in these matters.
Chien Chien looks like such a happy little dog! 12 years is a long time--that's a lot of love; that's a very strong bond. She's running free now, playing and waiting for you.