She's closed it off. I can only deal with the conscious mind, and if she's trapped in her subconscious...then there's nothing for me to read.

[ooc: Oh, yes, I do know! But Satori can't read Koishi's mind in canon. Quoted from the Touhou wiki: "Even her older sister, Satori, is unable to read Koishi's sealed-away heart, and doesn't really know where she goes or what she does there."]