If it helps to have another opinion on the possible age of this doll pictured ... based another WS'ers personal experience with this same doll ...
We have two of these beloved dolls here at our house. The first one arrived on Christmas day, 19 Christmases ago. Second one arrived the next Christmas for our 2nd daughter. The doll came in 2 sizes. Ours are the smaller size - for smaller hands. Toys R Us carried them. They were not expensive, they clean up great, have no "eyes, eyelashes, or hair", soft bodies, they came in blue or pink washable pj's, and they have lasted forever - both my daughters still keep their "babies" in their rooms. To both my girls, this is a very special doll - and both selected this one as a doll that they are keeping them for their own children someday. We also have American Girl dolls, this is not the American Girl baby doll.
Casey's age is right-on to have been the original owner. It's my opinion, this WAS Casey's doll. And, IMO it's quite possible, Casey was still attached to it.