It can be extremely difficult to split up a never-weaned mother daughter pair, more so than just bonded pals. There is a chance that you might be able to pair one up with a different pal but it might be kinder to find them a home together that is willing to work with their bond. Somebody out there would be thrilled with pony mascots, or willing to take on the rehab and training challenge to have a matched pair. Ringbone can be reversible but that is not always a sure thing and probably not the way you want to be spending your time and money. You certainly haven't failed them in any way bringing them back to health.

"It's really quite amazing what a horse will do for you, if he only understands what you want. 
And it it's also quite amazing what a horse will do to you if he doesn't." ~ Bill Dorrance