i second what rosemary has said it is the same with horses let them say good bye, they deal with it better, you will find the strength to get through for your other dogs, my old girl roxy is a rescue i also rescued her full brother, the demons from his past came back to haunt him and it was decided to let him go in peace before his mental state went to far and he reverted back to the shell of a dog that i rescued, roxy missed him terribly, that gave me the strength to get through it, as i had to be strong for her, and get her through losing her bro, i was worried she might give up but 4 years on she is still by my side, she has the incontinence problem you have mentioned, we get tablets from the vets that help it, may be you could have a chat with your vet, then maybe if she cant cope with being in the cottage on her own she could sleep in your kitchen, just a thought.
thinking about you all