After a quick Google search, I’ve found that on a few sites they refer to a “catgirl” as “catgirl” (noun, feminine).

On this site they’re talking about a game on steam that consists of catgirls.

You probably can keep catgirl but if you want a French word, I can suggest minette which means both a female cat and a young/pretty girl.

If you’re not going to use French in a French language text, you might as well keep the original language (Japanese) word like neko. Either way, chattefille is meaningless, but sounds cute imho, just like minette. Fille-chat is the comprehensive construction for the animal + girl composition you have in English : homme-araignée, …grenouille, …chauve-souris; you could use them with femme/fille. Plus a Wikipedia stub has fille-chat for nekomusume/nekoko and « oreilles de chat » for nekomimi (猫耳) which feels like a cute nickname. Furthermore searching for “fille-chat” on Images yields results aplenty along the lines of what you describe. There is nothing that catgirls does that couldn’t be sung about les filles-chats and therefore in my opinion the loanword is useless here; in fact before you asked I would have thought the catgirl was batman’s girlfriend’s sidekick-daughter… in any case I’d check for the age on her drivers license before selling her a drink.

There is no official translation of “neko-girl” in French, so you have some possibilities:

• You can translate it, as fille-chat. In French we already have l’homme-araignée for Spiderman, les hommes-grenouilles for people with a diving suit, etc. Chattefille sounds like a lazy translation for me, but nothing terrible.

• You can keep the japanese neko or neko-girl, especially if the game is designed for people that are fond of Japanese culture. This is coherent since it is a monster from a foreign culture, as for example you say a kaiju in both English and French to designate Godzilla.

• You can take the English catgirl (or cat-girl) if it correspond to a clothing that make the girl look like a cat, to make an echo to bunny-girl.