I thought Polly's transition from deranged drunk to calculating schemer was a bit too quick and seamless - imo that's a problem with her character in general: flip flopping between ruthless and pious/scrupulous. I'm also not too sure how I feel about her meeting with Changretta. Seems a bit extreme to sell out Thommy's life. He's family after all and I'd also expect that someone who is calculating as Polly apparently is again wouldn't sustain such a huge grudge from the near execution. It's also a bit paradox that someone is ruthless and cunning enough to deliver their own nephew, but also naive enough to believe that they will be safe after Thommy is dead.
Maybe it's a trap?
I also often wonder why Lizzy Stark has a seat on the board of a company that's so centered around the "blood" family. Back in s1 she was just a random whore. Then she became Thommy's secretary and feck buddy, but I can't recall her ever putting anything on the table beside that. No advice, no insights/opinions, no real handling of business, no plays.