The easiest way would be to just have access to AL's accounts (which I'm sure she doesn't have right now, given AL's control issues, but who knows what the future holds). She could take most or all of the money out of the account(s) while AL is still alive (or, hell, even after she dies) and AL's family really isn't in a position to dispute it. They might technically be entitled to all of it, but I can't see them trying to sue for it, especially if they don't know how much is allegedly missing. They'll take what they get (if anything -- and if Becky is smart (lol) she'll give them something) and go on a binge.
But there is another way for Becky to get her hands on that money. I don't know about Kentucky, but in a lot of places once you've lived together for a certain amount of time you're considered common-law spouses. Again, depending on where you are, this can qualify you for all kinds of things like division of assets if you break up (think of it as a common-law divorce settlement) and, of course, inheritance.
Yes, making this claim after AL's death in order to get her "estate" would potentially open Becky up to issues around having taken benefits while AL was alive, but that's a problem for future-Becky. Her clan seems like they'd be pros at the whole, 'unmarried when it comes to benefits, married when it comes to inheritance' kinds of schemes.
Better yet -- though insanely unlikely -- is for AL to just write a will naming Becky the sole beneficiary.
