Kaylee's mother had always warned her about taking gifts from people who wouldn't tell you why they were giving it to you or even how they got it.
River never explained how she knew the exact way Simon would touched her, or how she knew the exact words Simon would say in his mind, but could never quite say aloud.
Kaylee knew of course, River was a reader and a genius.
It was no trouble for River to calculate the how much pressure he applied to her skin or remember the angle his hand would lie on her knee or even listen in on their conversations to hear what Simon wanted to say and to recite it later in Kaylee's bunk. It wasn't even difficult for River to sound like Simon while saying it.
And Kaylee felt it was okay accept river's gift because she knew it came from a completely legal and morally… well completely legal place. And she felt no reason to ask why River was so concerned about how her brother touched Kaylee or spoke to Kaylee, or why River crawled into her bed at night to imitate what Kaylee wanted so badly for Simon to do.