I am so sorry to hear of you and your friend's loss. It is so hard to make decisions about our loved ones and hope that you make the right one.. They patiently wait for us up in Horsey Heaven and become our Guardian Angels awaiting our arrival..
Ziggy sounds like a really cool horse and Debbie is the kind of owner I'd wish for if I were a horse. A hug to her and to you. No matter how right the decision to euthanize is, it is never an easy one.
For me losing my horse was one of the hardest things I will ever go through, so I'm extremely sorry, but at least he can be happy again in heaven.
That is so sad, but it is always better to let them go in peace with you by their side instead of suffering.
So sorry for Deb's loss. Making the decision to put any animal down is not easy but must be made for their sakes.
I am so sorry for your loss. But I respect Debbie for cutting loose of her attachment to Ziggy enough to make a (hard)decision, that is inevitably the right decision. I am in those boots right now...and letting go of a horse you have loved and spent many years with is not easy. But sometimes you have to...