My heart is in my throat and tears are streaming reading about your dear Mona.
I agree that if the vet could be coaxed to make a housecall...this would be ideal for both of you. I have done that for pets who really cannot make the trip in.
I truly believe that an animal companion who has this much in common with us, and who has been with us through our good and bad days, is so deeply connected that not even death can break that bond. Try not to think of it as an end, but as a transcendence where she can truly be everywhere with you and at any time.
My Bridge dog, Shadow...he was the kind of dog who would've been happy to drop mid stride on the trail, or defending me, but he passed at our very kind vets' in peace, after weeks of illness where he could not even raise himself to a sitting position any longer and was in kidney failure as well...soaking himself, and a thin spectre of what he had been. It absolutely gutted us to have to say goodbye, but worse was how far we had let it go. I think my OH was hit even harder than I because he just couldn't say goodbye even as the vet asked if we were ready. I'd had to beg him to take him in.
That being said I feel it is not fair or helpful to yourself or the beloved friend to say, 'Oh we should've gone long before now', or 'maybe if I had just done things differently'... What is important is that you are going to give her this gift now and she will soon be restored to her young and vibrant self in the beauty and peace of Paradise.
I am so sad for you, because I know it hurts...there aren't words for how it hurts. You have all the vibes and prayers I can muster for a peaceful passing for her and comfort for you in this very, very sad time.
Bless you and (((((((((((((Huge hugs))))))))))))))) xxxx