Well, the answer here depends in part on which characteristics you're talking about, and what each person is jealous of.
Mercy, of course, is one of the emotional icons of The Witch of Blackbird Pond. Though her limited body gives her more reason to be jealous (as does the possibility of losing her love), she accepts, despite all.
Kit is jealous of the family's closeness and acceptance early on; it seems like she has not place of her own (and she doesn't, really), and so envies them.
Judith is most conventionally jealous. When Kit gets male attention, or shows pretty dresses, she flares with jealous anger.