Sadly i think.. it feels like a bug. This never happened in the past updates her quest Finished a long time ago, And there was no problems in her quest.
But when you play New game on this new updates her quest is.. Feels like broken. And i have talked about this patreon's and their reply was not what i was expecting. 
It turns out natasha was just request npc, that she wasn't so important in the story of the game.
I have been notifying this as a request to the dev Many times, But he doesn't give me a reply. like over two years lol ! 
That's what i'm talking about ! There is no less corruption route anymore ! She just go Full corrupted, Max breast size. There is a option to cure the tainted fountain make her not to full corrupted.
And her breast size will go down by one before max, it is in the walkthrough too. but No matter what you do even if you already cured the tainted fountain, she just go Full corruption.