There isn't anything inherently unsafe about using a dremel as a mini router. Basically think of it as cutting a 3" wide, 3" deep slot with your
1.5hp and a 3/4" bit, you will need to make about 100 passes per slot :). Since dremel's don't have much power and the bits are small and don't have a lot of mass they don't hit very hard when they do break so long as she is wearing safety glasses and not a low cut shirt like the girl carpenters she's seen on tv ;) Why not give her a handful of biscuits and let her cut biscuit slots with the dremel? At least have her try on a scrap piece so she can realize that it will take two hours of cutting or a dozen broken bits per slot.