Betsy was much slimmer than most other 8-inch dolls, like Ginny or Muffy, but clothing for Penny Brite (an early 60's doll) does fit her.
There is a fantastic Penny Brite site at http://www.voicenet.com/~rcfisher/pennyb/pennyb1.htm that shows all her outfits clearly. I have seen almost very one advertised as a Betsy outfit at one time or another on eBay.
This pink Penny Brite dress shows up on
Betsy all the time! It has a two-tiered skirt with floral embroidery
along the edges that looks just like some on Betsy's party dresses and
it fits her, so it is the one most commonly mistaken. I am trying to find
a close-up of the dress since the MIP image is hard to see detail on.
Image Copyright 1999 by snnfn4me1.
Used with permission.