Please help - cat with asthma and spraying problem

I'm requesting advice on behalf of my brother's cat. She has an issue with spraying everything, like the couches and the beds, and they are just about to get rid of her becuase of it. According to them they've tried everything.

A few months ago she also developed asthma. Every now and then she will stop and begin to breathe heavily with her mouth open. She can't play or run around because she will get an attack.

My brother and sister-in-law used to smoke in their home and stopped recently when she developed the asthma, but it has not gotten better.

She did receive a rabies vaccine shortly before the asthma. She had bitten my son when he tried to tear one of her kittens from her and the health dept had them vax her. So maybe related?

She's had about 3 litters of kittens...not sure if that's relevant. She's very small and has half a tail; probably because of some accident when she was a kitten, but I don't think it's natural. She's gray with darker gray stripes.

She is terrified of my son and my son (3) is terrified of her, they've always been scared of eachother. My son was not afraid of her for a brief period after she had her litter, but then she bit him.

In one of her litters she only had one kitten. That's about all the info I can think of...

Thanks,
Ana
:)