You may want to consider looking into 4-H. There are sewing leaders for the kids who are taking sewing who would be able to work with her, as well. A lot of people think 4-H is just for country kids and livestock, but there are a lot of other projects that kids can take in it .... I learned to sew from my mom and through 4-H, and it was a great way to do things! They do background checks on all the 4-H leaders to make sure they're safe for kids to be around.
Typically you have to be "nine as of Jan. 1st" to enroll in 4-H but many areas have a Cloverbuds program for younger kids. Your local Cooperative Extension Office coordinates 4-H in your area (you can probably look it up in the Government section of your phone book, under "County offices," probably county agent or X County Cooperative Extension, OR it may be under the name of your local land grant college, i.e., "Montana State University Cooperative Extension Service, X County.")
Several of the 4Hers here work with a specific leader (or even a community member who's not a leader) on their projects, aside from moms. Grandmas can also be a great option if there's one near you with the skills .... And, if there's a fiber guild or quilter's guild near you, they may be able to suggest a particular member who would be able/interested in assisting.