"She wants to fill up her wardrobe with new clothes."
Translation:Elle veut remplir son armoire avec des vêtements neufs.
Good question! I don't know! I suspect that there's nothing at all wrong with nouveaux. But my Larousse French-English dictionary (NOT Google!!!) tells me that "Neuf" refers to new, as in brand-new, while "nouveau" means new-style, new, recent, fresh, novel (also another, additional, or further; but those meanings don't apply here).
So in this exercise, perhaps Mme. has saved money for a while by buying her nouveaux vêtements at second-hand boutiques, and now wants to splurge on some special vêtements neufs, straight from the runway at a Paris fashion show.
Edit: I've had my French-English Larousse for a while and should really get more use out of it. It's a better resource than Google translate, and it only cost $1.95 new. Yeah, I've had it since les années soixante dix. So I'm old; deal with it. :)
Nouveau/Nouveaux: Masculine single/plural; Nouvelle/Nouvelles: Feminine/plural. Neuf/Neufs: Masc single/plural; Neuve/Neuves: Fem single/plural.
Nouveau/Nouvelle usually go in front of the noun they describe. Neuf/Neuve go after the noun. Why? Because French is almost as inconsistent as English.
Nouveau/Nouvelle refers to something new to you, though your nouvelle robe may have come from a vintage clothing store. Neuf/Neuve is newly made. Les vêtements neufs are brand-new clothes.
This seems rather late in the game to me, though, to be introducing this concept.