Hi!
The story is told from Den’s perspective, so it’s quite difficult to fully show Rina’s transformation. Her character is indeed built more on the player’s imagination. There are moments that influence her — sometimes it’s the manager, sometimes her audience.
Because of her naivety (similar to the main character), she falls for their influence, and we as players observe her transformation. I’m planning to release a short story that will focus specifically on the events around her decision to stay at her job or leave. It might help clarify her transformation a bit more, but I’m not ready to say when exactly this addition will be released.
As for the app itself, I’d recommend watching tutorials on Ren’Py and Python. I started with Ren’Py videos and then expanded its capabilities using Python. It’s worth checking out — it might give you ideas and solutions for your project.