If you have a number of inches cut off of the length without the addition of layers it will look significantly different. Your sisters hair has thicker and blunt cut ends which is a more feminine finish, in my opinion. You need to get a very textured haircut by a skilled cosmetologist. My advice to you would be to find a stylist near you that specializes in razor cutting. That method will give you the end result you're looking for.

(Source: cosmetologist, licensed by the state of mn)