I think the argument is focusing on the wrong premise (solitary confinement vs forcing an old animal into a social situation), when actually the case could be made on the grounds of facilities.
While Paignton does have a relatively modern house, newer buildings are now superior to what they can provide. I would argue that elderly animals, in the absence of health problems that would specifically prevent them from enduring a move, and who had responded well to the process of training for crate transfer, would almost certainly benefit from larger indoor facilities with more light, greater indoor areas on soft substrates, underfloor heating, indoor pools and showers, and perhaps mental stimulation from being in the proximity of other elephants. From there, it would be possible to judge whether the animal was interested in interacting through the barriers, or was more comfortable at a distance.
I would be very surprised if simple proximity to other individuals caused distress in an animal intelligent enough to understand whether there were barriers between them and another elephant.
With all this in mind, Noah's Ark, Blair Drummond (although climate is a factor still, despite the new house), and even Longleat should be ruled out only through a thorough process of evaluation by Paignton. Just sitting on their animal on the grounds that she is old and has eye problems is, IMHO, short-changing her if there is evidence that better indoor facilities in a temperate climate can really improve the physical condition of older animals.
I won't make the same argument on the threads about Katie in Blackpool, but the above absolutely applies there, too.
