"These ladies are model employees."
Translation:Ces dames sont des employées modèles.
There is no such word as 'cettes' in French. 'Cettes' doesn't exist at all in French!
Either it is for singular masculine 'ce' (or 'cet' if succeeded by a word starting with a vowel) or singular feminine 'cette', both refers to 'this' in English.
For plural masculine/feminine, it's 'Ces' always and not 'cettes', referring to 'these' in English.
I hope you understand the difference now.
According to this: https://www.thoughtco.com/cettes-filles-french-mistake-1369451 , simply because French is not logical (well neither is English). 'Ces' is the plural for both M & F. Not very comforting but there is is.
I would have thought that the 'g' of 'bangs' (goodness) would justify placing 'modèles' before 'employées'. I did this but was rebuked by Duo...