Taken from the Walk-Thru for Natasha:
6. The next day you have to repeat these actions and watch her drink and then when she's in her room from 4pm-20pm spy on her from her door. You can talk to her about her being a priestess during the day (while she's near the statues) to see how her attitude changes
7. At some point she will start to masturbate and after watching her you can enter her room.
8. At this point you now also have the choice to stop her breast grow. To do that buy a strong anesthetic at the shop and pour it into the fountain after midnight. This way if Natasha's breast haven't grown to max size she will stay true to her goddess. If Natasha ever goes to max you can still reduce and then expand her breast-size afterwards. But once at maximum her behavior will change forever.
9. You can also talk to pater Francis during the changes to get his reaction to Natashas changing condition.
Yes?
I did untaint the water at point 8, but you can't reduce her breast size.
The WT alludes that you could even if she is at max corruption, but I guess they can only be reduced if she is at max corruption. I don't really understand why.
I tried, after untainting the water:
1. Talking to her in the church, that does nothing
2. Watching her when she pays, that does nothing
3. Punish her, that does nothing
4. Have sex with her, that does nothing
5. Leave, does nothing
6. BJ, increases her corruption.
I don't really see what you want me to do then.