Poor little mite, we've been there and I feel for you both.
You say that there's no way it would be practical to have another dog - may I ask why? Reason why I'm asking is that this was what brought Max, my Lab X, out of his very similar sounding grief when we lost, very suddenly, his Staffie X pal when Max was going on for 8 years old. I wasn't seeking to adopt a puppy but an older dog, yet found a 6/7 week old GSD who turnd Max from a desperately unhappy, grieving dog into a joyous, bouncing, playful pooch again.
If a long-term companion isn't possible would fostering be an idea? You could chose the type of dog you foster, all food and any vet treatment would be paid for by the rescue and they would suggest a dog who needed your help for the period of time you considered suitable. You might foster just one dog and then leave it at that or foster one, then another and so on, you might choose to foster long-term or short term.
For example, I've fostered dogs short-term who have had homes lined up but are in need of care until the new owner comes back off hols, those which were merely waiting to find the right permanent owner for an indefinite perod, and my current boy, another GSD to add to Max and my younger GSD, is a (very, as in he's mine in all but name!) long term foster dog, here as he hates kennel life but no-one wanted to offer him a home because he has epilepsy.
Others volunteers for that particular rescue have fostered dogs who don't fare well in kennels in the winter (Greyhounds especially suffer the cold, for example) and youngsters who need bringing on and teaching/reminding what a home life is all about.
Might such a thing help your poor girl?