IIRC the BB is his only "pet," the others are full-fledged girls. No info yet on how the Imp would react to another "pet" being kept somewhere else.
Well I feel it's less about jealousy that she disappears & more about not causing MC any undo relationship stress. Every girl she disappears around are girls that would probably react rather poorly to MC having a sexy demon following him about.
Notice she dosent hide from Erevi, ED, BB, Venomina, Shakala, GD, Sequoia, Obeah or the Vampires. These are all characters who have no issue with such entities & fully accept that MC is fucking around with other girls & monsters (heck one could argue the Goblins & Vampires are monsters).
If the Familiar disappeared because she was "jealous" then she would disappear around them as well. But she dosent.
Instead it's more a convenience so MC dosent get into any kind of trouble. After all she wants to make herself useful & desired by her master, not be a hindrance.
So if a Catgirl was no smarter than the BB then it goes to show that the Familiar would probably not disappear around her because their is no issues to be had.
Also would be cute to have some lil kittens running round the MC's House as well. Mabey we could by them scratching posts, beds & toys from Harold