I don´t know very much about theraphy with animals and I haven´t got any strong theory about this, but when you are working with people who like or animals which like is more confortable and its easier learn things.
As we can see in lots of documental or tv programs animals can help a lot to humans, the typical image or video is a dog helping people in nursing homes with elderly people or in a shelters with children. they are really useful in a emotions development work and with people who need special education. In that case, the animal is a Dolphin.
In that kind of situations, people get very involved and Nikki´s mother could get a lot of money. I am sure that she had to work a lot but, in the world there are a lot of cases, similar like the case of Nikki, that they don't have enough lucky and they continue with their problems. Maybe because they don't have nobody to help them or they couldn't move as much as Nikki´s mother because they don't have enough resources.