If you're both going to ignore the tsundere clues, then that's on you. KrayZ33 and I both spelled them out.
He even noted the difference between how she's bullying him and how it went in the past. She's making him look at her, and softens up when he tries to retreat.
There's definitely mutual stuff going on. Her blush intensifies differently when she's harassing him and when she's trying to trick him into flirting, only to cover it up with more teasing.