
Because he's twisted and she doesn't have the advantage YET. She has to be 100% sure with him. So long as she's "Lady Veronica" she is reliant on their funds and Veronica's name. There's little reason to subject yourself to more trauma and mind games when you haven't consolidated "L" yet, completed your goals and have a back-up plan. Going head to head w/ ren? He'll use it as blackmail material.
What's worse is he now thinks the crown prince is competition which increases her value to him past the mystery. All in all, she's still a mouse and he's still the cat, and at this point killing her would benefit him more.

It's like, a bad idea X10. The problem with Ren is that he judges worth by amusement, and being in a league with a guy that doesn't follow logic but his own, fickle emotions is asking for him to stab you in the back. Like some guys can step back and let it all unfold but Ren? He wants to have fun.
Another thing? He isn't supposed to know she's not the real lady Veronica. God, imagine how much worse he'd be if he found out she was a commoner, much less one in a noble private school, much less one the crown prince has taken a liking to, much less one that actively avoids him. Goddamn he isn't someone you can bargain with.
i mean Ren hates the grand duke so much as well as the original veronica.. so i guess FL has a good chance of forming alliance with him if she reveals the truth.. but why wont she work with him? this is the only thing i dont get. yes she was bullied before by ren but that's because ren thought she was working for the grand duke by pretending as veronica. if they just work together, i think she has better chance on being alive.