Essery felt herself blushing at the compliment, it wasn't entirely unexpected but it was so... straightforward. She wasn't sure Severus knew how to beat around the bush at something. It also didn't feel like empty flirtation - or like flirtation at all - and that honest quality of it made it... well, it made it seem more important.
"Well..." she said, quietly suddenly and looking down to the board herself to hide the blush. "Thank you. "