A few onlookers noticed that it wasn't the first time the princess had cleaned off the knight. At the hunting competition, she showed the same behavior. Some in disapproval of the couple believe it to be possessive while others looked on with envy.
If her brother or father were around they would certainly be disturbed by her putting herself in a position lower than a peasant. Since she was doing it on her own accord without being asked, no one present said anything.
At her slightly annoyed expression as she finished wiping the mud off of Henry's forehead, he stared into her eyes with an intense expression as he assessed the situation. She cared enough to clean him off but was still obviously upset and he didn't fully understand why.