Mrs. Slipslop displays a very particular brand of pretentiousness. After years of exposure to Lady Booby's whims, Slipslop uses big, made-up words to make people think she's super smart—only most of the time, she totally misuses each and every one of this words. Let's be honest, though: malapropisms or no, Slipslop's got plenty of smarts. She's the crafty kind, even if you wouldn't guess it from the airs she puts on—like when she says she is "confidous" that Lady Booby would not leave Joseph behind when she goes to London (1.3.10).
Like mistress, like maid, we guess. At least that's Slipslop's approach to trying to seduce Joseph. She's described as "a hungry tigress, who long had traversed the woods in fruitless search" after seeing Joseph emerge from Lady Booby's bedroom (1.6.8). While Slipslop's not quite as committed as Lady Booby is to vying for Joseph's affections, that might be because she knows when to bow out. When it becomes clear that Joseph's just not that into her, Slipslop uses her wiles instead to manipulate Lady Booby into re-hiring her.