Diminutive, feminine (in some sense), both. In the One Big Happy strip of 3/4, in my comics feed on 3/36:
(#1)
In modern English — that’s important — the suffix -ette has two relatively productive — that’s also important — functions: as a literal diminutive, referring to a small version of the referent of the base to which –ette is attached (“diminutive” suffixes can have a variety of other functions, notably as expressing affection towards this referent); and as a literal feminine, referring to a female version of the referent of the base to which –ette is attached (“feminine” suffixes can have a variety of other functions, notably as markers of grammatical gender (ggender), as opposed to natural, or sex, gender (ngender); English doesn’t have ggender).
The big generalization about modern English is that –ette attached to bases with inanimate reference (like disk) tends to have the literally diminutive function (diskette), while attached to bases with human (or, more generally, higher-animate) reference (like usher), –ette tends to have the literally feminine function (usherette). Novel formations follow the generalization: a spoonette would be a small spoon, not a spoon in female shape, or a spoon intended for use by girls and women; while a guardette would be a female guard (perhaps viewed dismissively or derogatorily), not a miniature guard.
Ruthie’s brother Joe apparently fails to appreciate the big –ette generalization, and takes a bachelorette to be a miniature bachelor, rather than the female counterpart of a bachelor (in Joe’s terms, a grown-up girl — a woman — who isn’t married yet).
