Let us speculate. There is really only 1 clue.
What if Jill is not Royce? In the introduction of EP7, Jill bears more resemblance to Melanie than to Jill. What if Jill is actually Melanie and Melanie is Jill. And why?
Lana was banished by her parents. The reason will probably be that she was a party girl and her parents didn't approve. That's what Lana's sweater suggests. Now Jill (Melanie) wants to escape her golden cage at college. Melanie (Jill) switches places with Jill (Melanie). In Melanie's and Sarah's room there is also a picture with hearts in the background, which we also see in the intro. Why is this picture not in the Preps mansion? Actually, it's quite simple. The Jill in the Preps mansion is not a Royce. Tybalt can have this Jill in the Preps mansion at his leisure. That's why Jill had an engagement ring on her finger in the library scene in EP1, and it was from Tybalt. Only Jill wants the MC because he is richer than Tybalt. Jill could be the complete fraud.
But then why are Amelia and probably Geoff at the concert? They don't want to see Jill, they want to see the MC. The MC could be the child of Amelia Royce and/or Geoff Burgmeister. Yeah, I know, incest. But if the MC turns down Quinn's offer and the MC isn't with Sage in EP4, the MC doesn't even get a chance to fuck Melanie, and thus there is no incest.