знай
ты должна знать
тебе следует знать

In English, YOU SHOULD KNOW is a snarky retort that basically accuses the listener of the same “sin” they’re pointing out in you or someone else: [Anna to her younger sister]: You’ve gotten really pretty over the summer and all the boys at school seem to have noticed. But you don’t have to talk to EVERY boy that looks your way. Remember, a bad reputation is hard to shake. [Younger sister]: You should know. (= you have an appalling reputation yourself!)