Her former master used to speak in rhymes, so it can be suggested that it is Bellegar from Divinity OS 1.
(The magisters guarding the front entrance to the ghetto and the patrolling magister are of no concern.) The easiest way to escape with the cat quickly involves the quest called The Teleporter. You can converse with it using the Pet Pal talent, but it doesn't tell you much and seems confused. Black Cat is an NPC in Divinity: Original Sin 2 (DOS2) which follows the first character in party it sees.
