For many weeks Amanda, and by extension McCrae, knew what was going on in every corner of the house. But now they are suddenly so far out of the loop that it's hysterical. Since they still haven't figured out that they've lost their pet rat Andy, they think that if they can get the right repl-nom on the block there's a chance that they can both stay.
And since the boys of the Exterminators want McCrae out more than Amanda, they came up with this crazy plan to get him to use the veto on Amanda. It was such a wacky plan, I couldn't even explain the logic of it, but basically he was supposed to offer some deal to GM that he'd veto Amanda, if she'd put up Elissa. I can't figure out what was supposed to be in it for GM, but it really doesn't matter. Because no matter what he said, McCrae never had any intention of using the veto on Amanda. He's not that stupid. As a BB fan he knows that you always save yourself if you're on the block, unless you're well prepared to walk out the door.
And GM wasn't really listening anyway. She's loyal to the Exterminators, but she also knows she's got something good going with Elissa, and she's not going to throw that backup plan away. Plus by letting McCrae see her as with Elissa, if he wins HOH he'd maybe nom her against Elissa, but GM would be happier about that than to be against one of the bug boys.
So, it's basically a done deal that McCrae will veto himself and GM will repl-nom perma-pawn Spencer tomorrow. And since there's next to no chance that Spencer will go, it'll be Amanda heading off to jury on Thursday.