The speaker addresses a younger half-sister, probably judging by the line about "sisters by blood, maybe" and the shared father who is mentioned only vaguely. She sees herself in the girl: the same face, the same restless streak, even the same urge to steal that she had as a child. Calling her a "pretty little monster" sounds harsh, but it reads more like recognition than cruelty. The speaker knows what that wildness leads to.
The feelings are mixed. There is wariness, some bitterness about the father, and a sense that the girl's future will be hard. Yet the ending softens things. The speaker says she doesn't hate her, only wants her to know what's coming, and wishes her luck. The mood is dark and teasing at first, then quietly protective, like a warning from someone who has already walked the road and can't quite stop herself from caring.