That is really odd thing for your mom to say. I have to admit, I usually don't tell people to disobey their parents. However I am going to have to tell you to not listen to her. Hair should be washed every other day, to keep it clean. Yet you shouldn't wash it everyday. If you don't keep you hair clean, your hair is at risk of getting hair lice. Not a pretty picture. Now maybe if you hardly have any hair, maybe once a week is fine. But if you have quite a bit of hair, you need to wash it (at least 2 times in 1 week). I wish you all the best.