The beldam gets a lot of things wrong in her other world, but she seems to hit upon something important in the alternate versions of Miss Spink and Miss Forcible.
They were thin, and pale, and quite pretty, and had black button eyes.
The new Miss Spink was wearing green tights, and high brown boots that went most of the way up her legs. The new Miss Forcible wore a white dress and had flowers in her long yellow hair. (4.58-59)
The two women, in the real world, seem obsessed with their glory days as actresses. In fact, it's pretty much all they talk about. So it makes sense, in a creepy way, that the beldam would create versions of Miss Spink and Miss Forcible who are young actresses. Of course, the actresses only perform for an audience of dogs, but hey, we shouldn't knock their success.
Coraline doesn't find this set-up appealing. She finds the younger versions of the women, and their entire show, quite disturbing. The thing that seems to freak Coraline out the most is the fact that the show is unnatural: Miss Spink and Miss Forcible aren't supposed to be young anymore; dogs aren't supposed to talk and be audience members; and the two women definitely aren't supposed to turn into a freakish blobby cocoon.
In the end, we feel like Miss Spink and Miss Forcible wouldn't want to be young performers again either. They might talk a lot about the past, but the two seem to enjoy their current lives pretty well, too.