Thanks for the feedback. This is the free version (non-elite). The non-free "Elite" version has additional content that is fun but not critical to the story. It's available on steam or patreon.
The patrons and steam supporters really drive the content of the game. They opt'd to see Tragedy of Medusa (the prequel to EG) and soon Athena's Revenge (the sequel) produced in place of adding additional content (ie Diana) to Euryale's Gambit. I will fix the option in the brothel in the next update.
Ah, so the Elite checks are a hint to a different version. This hasn't been explained anywhere, iirc. With "fixing" you mean to remove Diana, I guess? I'd love to support you, but I'm not the biggest fan of monthly payments for everything. Also, Steam won't let me buy the game in my country. Would it be an option for you to sell the game also here on itch?