I Have a Difficult Mother-in-law

I think I might try to steal my Mother In Law's dog when I leave here (I currently live in her house).

She is highly neglectful of her pets (feeds them at her convenience, even if it means skipping a day...she never bathes them, grooms them, or trains them...and she never holds them or pets them), and this particular dog has bonded with me. If there is any way I can take it when I move without her knowing, I absolutely will. But she is an eagle-eye about what she considers "hers", and so I'm very doubtful I could pull off a dognapping.