and one could not believe in a mockery if one knew it was such. とはどういう意味ですか?

“They will talk to you tomorrow,” Luna said, watching as the kitten in the stars yawned and stretched itself. /They always do, and then take them away from me./

“Who’s gonna talk to me?” Pinkie asked. “Oh! You mean Elder Moonshine? She stopped by our house yesterday and said tomorrow’s gonna be a special day! I’m going to start helping with Seeking Night!”

Luna did not reply. She knew enough of Seeking Night thanks to dreams of foals and Pinkie herself. A celebration—or mockery, more like it—meant to treat the imprisonment of her and the others as a little game for foals. At least foals truly believed they were helping the princesses, truly believed their little actions would set them free.

But when they turned thirteen, they were invited to help with the festivities, and one could not believe in a mockery if one knew it was such.

There were a few foals, every now and then, who struggled with the idea that she was not “real.” They’d let her into their dreams maybe two or three weeks following their birthday, but eventually the doors would close, and each time, Luna felt her dream of escape dying a little more.