How can she know other person's intention? Is it common to say a sentence like "You don't want ~"?
Native speaker’s answer
Rebecca
"You don't want~" is not actually a guess of someone's intentions. This commonly used expression means "don't" and is meant to be helpful advice or a polite warning. We can understand "you don't want to go that way" to mean "don't go that way." Ex: When you're cooking, you don't want to leave the pot unattended. (Don't leave the pot unattended.) Ex: When taking exams, you don't want to spend too long on one question. (Don't spend too long on one question.)