Tiny versions of minifigs with regular minifig heads are called microfigures,
so logically you'd call tiny versions of minidolls with regular minidoll
heads microdolls.
I had never actually used it as a search term (and don't really care either
way), but is there a reason for not using the correct (according to LEGO) hyphenated
term Mini-doll?
Although, both Mini-doll and Mini-Doll are used here:
I would call them Mini Dolls because they have mini doll heads and hair. They
would just need a word in their description to indicate that they are chibi.
They are a little off book in having apparently solid bodies, but Minifigs come
in 4 different heights because of their different legs and they are still minifigs.