Logic is independent of knowledge...
While this may be true, nothing in the story so far would lead one to believe that Lily would have this type of insight into business development based on her previous job or life experience.
However, what could make that whole part of the conversation more believable would be a simple line of inner thoughts for Lily before giving her answer how she remembered reading about the topic while studying at the library. At the moment it feels like because Marcus told her to act like his right hand she magically gained business acumen high above her pay-grade or experience.
Please don't take my criticism the wrong way, I love Lily of the Valley. It's still one of my all time favorite games, even with the slowdown in updates, but at least the updates always had the same level of quality up to now, especially the animations.
Like I said, it's just painful to see something that had consistent high quality become something that feels rushed, resulting in Lily losing her identity in the process.