I was just looking at my American Girl encyclopedia and saw some early sketches for "Kirsten."  When I used a loop magnifying glass to zoom in on the sketch, it said, "Rebecca."  I wanted to know more, so I researched it and nothing was shown.  Photos of the book and page are attached below. What name do you like better?

Sorry that you can't see the second photo very well. The letters are so small so it is kind of blurry.