Delightful. I continue to marvel at how well Beholder writers take "impossible" pairings and make them totally credible. Your Arabella is a thing of beauty, slippers and all. I love her matter-of-fact, self-contained, contented way of looking at world, cats, and wizards. Sirius is nicely IC, too.
Lines I love:
With just the beginnings of a plan he began to feel cocky again. He was at his best improvising and making it up as he went along. Preparations were for Ravenclaws. Plans were for Hufflepuffs. And really detailed plans were for Slytherins. He was a Gryffindor and wild swoops of chance were his element. This line is just SO Sirius -- annoying and insightful at once.
Needless to say that was as good as threatening to tell the entire village that their family had produced a squib. She'd made the message even clearer by writing with a muggle pen instead of a quill. It was a cruel thing to do, but needs must. It's with lines like this that you characterize Arabella so well. I love stories that show squibs being perfectly happy with themselves and not the pathetic losers that magic folks apparently would prefer them to be.
Wizards, she thought, were just like cats, sure they were the center of the universe and sure they were superior to all other life forms. It would be funny if they weren't so deadly serious. Love your Arabella.
She had always been a sucker for cigarettes and good hip bones. Yes! This sounds like a line from a classic film noir. For some reason, the whole story gives me that '40s hard-boiled vibe, of tough-minded men and women meeting and parting and holding their own. Except that Sirius is not as tough as he thinks he is, and Arabella probably is.