Prototype of Lizzie Hearts doll and the Spring Unsprung playset >>> Pictures from mojukie on Instagram
I remember I've saw this prototype doll & playset on a website in 2020 (there was also a prototype doll of Kitty Cheshire basic with the same bracelets she has in the webseries and that the doll was supposed to have).
As you can see, the colors for the clothes and accessoires of this playset are totally different. We know now, thanks to Monster High's interviews from creators, that they carry out tests with scraps of fabric and plastic accessories of a particular color to make the first prototype dolls. That's why the colors are not the final ones and that the book doesn't have the final illustrations made by @lisaartwork (that you could see here, here, here and here).
Thanks to the VK group BlogDolls: новости мира кукол for the discovery!