Has your mom tried familysearch.com? There is so much information, there! Free, too!
I don’t know what resources were used. This turned into a joint venture with some of her cousins and their kids which ended up as a family reunion out in AZ about 10 years ago.
Mom’s got a photo of herself and some of the other family standing in front of her uncle’s old house in a podunk desert mining town where she and my grandmother stayed while visiting in 1938.