Training together over such a time, it was easy to get used to how someone moved. Even when trying to catch them off guard, eventually those will become known and expected too. So Vegeta is well used to that kick of hers, is ready to deal with it as it comes his way, and is pleasantly surprised she decided to mix it up with that fake out then follow up hit. So he won't take away that satisfaction of it landing, even if it's against his raised forearm he brought up to block it.

It's followed up with his own punch, swinging around with his other fits to aim for her side; half meant as a punch to land a hit, but also as a force to push her back, to make her find another way to come at him.