Why do my hair grow faster then my mothers?

Me and my mother have African American hair. I used to have very short hair and my my mother had short hair at the time i had short hair. So we started using the same products like shampoo,condition, relaxer, oil sheen, hair growth grease and alcohol free hair gel. We both took really good of our hair in the results of 6 months later, my hair had already touch my back. My mother hair grew but it didn't grew long and fast as mine did and she took care of her hair like I took care of mines. I don't get it. Do some people hair just grow slow and some fast??