Someone who always gets what she wants. She is always right and always wins. She is one you can count on. She is so easy to get along with and she's really pretty. You will always have the best time with her no matter the situation. She can keep all the secrets you have and always falls for the wrong person. She is definetely bestfriend material.
person 1- dude, that's my best friend.
person 2- that must be sierra then.