Neat pattern on that link above!
One piece of advice. If it's going to be a lap quilt and used a lot - don't use the shirts for the back. Use something more sturdy to take the abuse that a lap quilt gets. The lap quilts that I have made that have fleece or minkee on the back do not have any holes or fraying. The ones where there is cotton fabric for the backing are frayed and with holes after a few years. I vote for brown or blue minkee for the back so she can cuddle up with it.