You bet! One of my parent's friends had a toy poodle that weighed maybe 5 pounds. They never had her fixed, and whenever she came into heat, they had these diapers for her. Our Maltese "Daisy", when she got up to 18 YO had to wear diapers at night due to incontinence. Baby diapers with a tail hole, essentially.

I would have put her down earlier, much as I loved that little girl. She was done long before my wife could let go. I thought about euthanizing her myself, given the suffering that I perceived that she was suffering. But if I had botched it, I'd be pretty damned mad at myself.