Seeker, even animals have to pay the consequences of their actions. IMO, it would be more cruel to keep her tied up. Dogs get mean when they're tied up all the time. I know I would, too!
I'm glad I'm not in your position, though. It's a tough place to be. But I certainly understand!
Best wishes to you in this difficult decision.
__________________
Psalm 119:105 Thy word is a lamp unto my feet, and a light unto my path.