Ok, here’s what I remember. the main characher is a girl maybe 13 or 14. Her little dogs goes everywhere with her and has a limp. Turns out when her dog was a puppy she got annoyed with him and smacked him with a broom, and he’s been limping ever since. She has a guilty conscience about the whole thing.
Girl lives were her mother, or maybe aunt? and they are fairly poor. At one point she finds $5 on the street and its a big deal.
Again, at some point in the story Girl befriends a vet and he agrees to fix the dog up (why? I don’t recall. Maybe they do him a favor in return?) dog is all better! Guilt resolved!
I don’t believe it was a historical novel, but it wasn’t set in the 80s or later.