That was the bare minimum of decorum for professional chess. They're required to shake hands, say congrats, etc. It's not like say, Yugioh where not shanking your opponent in the parking lot after the game is where the bar sits, or professional VGC Pokemon where comp espionage is so prevalent that some people literally go undercover so their comp isn't suss'ed out before the event.

Chess actually has behavior standards, and she tiptoed the line on it as close as she could manage.