First I would like you to keep Ladylaw's offer to assist as a local resource in mind.
Now as to "A friend of mine is legally (though not completely) blind."
If your friend meets the criteria of working with a reputable organization she may be interested in a Guide Dog which are normally Labradors, Golden Retrievers, Smooth Coat Collies and German Shepherds or a cross of Labrador/Golden Retriever.
A reputable organization will need to know that:
1) She falls within their perimeter of less than 20/200 vision in the best eye with the use of corrective lenses and/or a less than 20 degree field of vision.
2) She will also have to have successfully completed Orientation and Mobility (O&M) training with the long cane.
You also said, "She is afraid of big dogs that jump on her. " This would not be a problem with a well-trained Guide Dog as they are first raised with organization supervised Puppy Raisers for a year or more and then worked under professional Guide Dog Trainers for approx. 4-6 months before the new handler is introduced to their prospective team member.
If her depression is caused by her lack of vision then she may be helped by a Guide Dog but that would have to be determined by herself, her therapist, and the Guide Dog organization intake staff.
Now if her depression is more severe (which would be determined by the professionals involved with her care) then it is possible that either an Emotional Support Dog (ESD)
or a Trained Companion Dog
may be of help. Just remember that those two are not Service Dogs and the owner does not have the rights that a handler of a Guide or Service Dog has.
You also posted, "as a sort of treatment for her depression. Having something that cares for her/depends on her, etc." This in of itself would not qualify her for a Service Dog as the Dept. of Justice has stated in their definition of a Service Dog that, "the provision of emotional support, well-being, comfort, or companionship do not constitute work or tasks for the purposes of this definition.” Again in this case an Emotional Support Dog or a Trained Companion Dog - on what you have posted - may be a good choice for her to look into.
Dept. of Justice Definition of a Service Dog
A recent thread on Trained Companion Dogs
And a recent thread on Emotional Support Dogs