How about a very basic but versatile block like a half square triangle. Using layer cakes, she could cut down each 10" square into 4, then do the parallel diagonal stitching lines on pairs of 5 inch squares to make 4.5" finished HST. Or she could half the 10" squares, then half those again and have quarter block triangles. The layouts for HST or qST are plentiful, giving her lots of design opportunities.
RST