well i guess she telling her i just need to make you fall in love with me somehow means that the succ girl is already in love with her
Everything a mindreading parasite with vested interest in manipulating you says is obviously and intrinsically suspect as fuck and Shitara's clever enough to realise this.
Not that it much matters for the end result, of course, but at least she knows better than to just believe whatever Sakihara tells her.