Thank you so much for your lovely comment! Dolores, completely vile though she is, is fun write. (If your idea of fun is feeling vaguely wrong and dirty.) Considering how she tried to use Veritaserum on Harry in OotP, I thought it would be plausible if she tried manipulating someone she considered the weak link in the chain to get the information she wanted.
I'm glad you liked the cats, they insisted on having a big part in this :-)