How would you feel about a hearing dog for her? One of my dogs is a retired assistance dog and it's really amazing to see what they can do.
I can imagine how being deaf and alone at night could feel like being in a sensory deprivation chamber.
However, for a little girl who doesn't really need to be "independent" to the extent that adults do, a regular dog might work too... there are many dogs which have been bred for hundreds of years to be guard dogs or watch dogs (a lot of the smaller yappy dogs were) so they're very alert and react to sounds around them. This might be very comforting to a deaf person to be able to "see" sound.