Did a quick check of all the previous chapters and this still doesn't make sense. Those two girls were never close, and Chizuru clearly believes she's the favourite. I suspect she believes that she's just too whimsical, but the date already proves who can connect well with Ryunosuke. Rooting for someone who has the least chance in making all three happy seems like a bad move. Especially after laying down the gauntlet. Gives the ones who are in it for the money a better chance in succeding.
Would've actually been more acceptable if the reason was money. Even if Ryunosuke loose all his inheritance, at least Reika would've been able to love and provide for him.😅