I’ve done a lot more research on this subject than probably anyone should and I’m pretty sure the answer is a depressing “no”. I’d love to be proven wrong but it annoys me that Carmella Creeper is a “cousin of Franken Berry” rather than a standalone character like the others.
What does make her stand apart from the other Monster Cereal mascots is she’s not based on a movie character. That’s something that makes the rest of that gang unique: there are some cereal mascots taken directly from pop culture (the Flintstones, Mr. T, Baby Yoda) and a lot more that are made up just for the brand (Tony The Tiger, Dig’Em Frog, Cap’n Crunch). The Monster Cereals reimagine Dracula, Frankenstein’s monster, ghosts (or The Invisible Man, though Boo Berry is given the voice of Peter Lorre, not Claude Raines), the Wolfman, and the Mummy (though Yummy Mummy is given the voice of Harvey Fierstein). I haven’t found any other cereal mascots like that.
I’m sorry to hear that but if they have The Monster Mash in there it’s about 50% Carmella Creeper cereal and 50% gray pieces for some reason. It’s not, as the box would suggest, a mashup of all the different cereals.