The biting thing she said began a few days after she rescued him a few years ago. And it has happened several times.

I don't think Busta was biting her because of pain. He didn't have the back issue until recently. My Friend has good energy and is a kind loving soul, so I'm surprised the dog nipped at her.
I didn't have a problem with him, but I was doing Reiki on him. Its a form of holistic energy work. I came from a place of calm peaceful energy so the dog will be calm and relaxed. I was up close, had his face in my hands, face to face with him, calmly talking to him and putting my hands all over his body. Not so much in a petting motion but placing my hands in an area for a few minutes then move it around to another spot. I do understand dog telepathy so I was able to understand his energy. I think he has jealously issues with the other dog. My friend ((had)) another dog a Yorky. She had all three of them at once. The Yorky passed away this year and now its Busta and Molly left.
It also might be that she gives the female more attention only because she hasn't had a biting issue with her? I don't know. Molly is the Queen Bitch in the house.

I could see that she ruled. Maybe Busta has issues stemming from a dominate female?
I'm going to ask my dear friend the reason 'WHY' she won't get him the wheelie cart.