I don't recall it being that hard. You can only ask the witch one Q a night so keep asking. And it's best if you've visited the place where Fina is being held before asking the Q. Krowly should talk to himself that he needs to grow boobs first.
Harvest mandragora at night. It's the plant with jagged edges. All over the place, if you know where to look.
https://f95zone.to/threads/warlock-and-boobs-v0-335-7-boobsgames.18692/page-66#post-1875891
And get Wake's walkthrough, it is more up to date than the f95 one:
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Finally, in the cheat room in Krowly's basement, there is a 'grow boobs' cheat.