I'm not sure what twist you're referring to. Anton goes through with Claire's demand, is killed, and Claire honors her side of the deal and lavishes riches on the town.
"...everyone finally shut up, and the audience could enjoy the beginning of the Anatevka Pogram in peace."
I interpret it as that she's finally happy that she's received her wish of having Anton with her eternally. She's dressed in black with her "natural" hair, no need to dress up and show off now that she's gotten "justice." She will be forever happy with her lover's coffin in Capri, a fate that Anton accepts in "In The Forrest Again."
It's like the little insert in the Playbill - what's better love or revenge? Claire gets both. She loves Anton too much to be without him for eternity, but she also still can't forgive him for what he did. She gets her revenge by the town killing him, but also gets to make him "hers" forever at their gravesite in Capri.
LarryD2, that's very much in line with how I interpreted the final scene with Chita. The change of costume from white to black to me was very pointed in its suggestion that Claire, too, has died and that she will be joining alongside Anton in Capri.
"I actually asked Chita about this. She said "At that point, she doesn't need to hide anymore. She can reveal who she truly is to the town"."
Thanks for this info! I was so mesmerized by the show I really didn't give that change much thought. I think I dismissed it as the passage of time or something. Regardless, I loved the musical and Chita of course.