I always got the impression that Dain touched her this way since they were much younger. And that it wasn't until the last time, when he was feeling whatever way about her being close to Xaden, that he decided to invade her privacy and found something. Like he respected her privacy until he decided that he knew better. Dain is a brown noser, not a slimey rat. Stealing her memory of Athbyne gives "I was worried/jealous and did it for your own good."