That is so sad. Some people can just abuse, neglect and then get rid of their pets like that. Don't think they even think of her as a pet poor thing
Your mom is really an angel to take this dog in and give her some love.
Just being a little informative, I remember Stephen Coren said that dogs can adjust well to being blind but in the house use scents. Training can be done to differentiate bad scents and good scents, you need maybe 5-6 different scents. The bad scent can be used for just before going down the stairs so that she knows and won't fall down the stairs. Another scent can be used for her toy and bed. I even remember him using one scent for making a trail from the house to the tree in the fenced-in backyard so that she can make her way out and come back by smelling the scent.I am sorry if I say too much, I just hope it'll help your mom. Keep us updated on the baby. At least from now on, she'll have a better life.