I agree with everyone else ... on letting her pick her colors but my advice would be cut 2.5 inch wide strips of your stash and let her pick the strips she would like to use in her rail fence or log cabin.... then use a multicolor print for the border or black (teenagers love black) Since she is a newby and probally does not know how to use a rotary cutter or how to sew a 1/4 inch seam ...practice first on some scrap fabrics.... make sure they use the same machine throughout the sewing of the quilt. Show them a pic of the quilt and let them know it will take more than one hour to make the blocks allow extra time because it always take more time... the reason I know this is because I helped teach teenagers and younger to sew quilts and pillowcases and lunch bags... Summer quilt camps for the kids...
hugs and bless you for doing this..