I think it's awful that she's doing this. It indicates to me that she's really mentally damaged in some way in addition to being emotionally screwed up.
While the dog is probably not suffering or in pain, she is making the dog unadoptable. It's like teaching a parrot curse words, not harmful to the bird at the time, but making the bird unadoptable. Teaching a dog to do something like this is going to make nobody else want that dog if something happens to her.
Plus what if this woman has another child? Will that child be competing with the dog for milk? I hope she doesn't have other children until she gets well anyway, but it doesn't look like she's even seeking help.