Every friendship starts as just that- a friendship. However, every once in a while you strike gold and find that person who's weirdness is perfectly compatible with yours, and that person becomes your person.
Everyone has friends, some people have best friends, and a few people are lucky enough to have their own person(s). I know Meredith and Cristina have each other, but I believe you can have multiple persons. I believe you need that person who will tell you the truth when you need to hear it, but also that person who will make you feel better in a time of despair.
When you give a girl a person, you give her the best of best friends. You may have known your "person" since preschool or may have met them in college, but either way the friendship is so pure. They're the first person you want to tell all your big news to, the shoulder you cry on, your go-to for a big favor, and your keeper.
When you give a girl a person, you give her the ultimate adventure partner. Your person goes on family trips with you. They go with you to get ice cream a mile down the road. They ride with you to go pick up pizza. Y'all go on random road trips to hit the sale at Ole Navy. They take you with them to their brother's ball tournament. No matter what you do with your person, you do it together.
When you give a girl a a person, judgement in non existent. You can tell this person anything and everything and no judgments will be made and your guard can be completely down. Nobody will listen or respond as well as your person.
When you give a girl a person, you give her a reason to never give up. Y'all go through everything together. You have fought, spent weeks without talking, and seen each other at our absolute worst. No matter what, you always come back. You never ever give up on each other, and sometimes that's the best reason to not give up on ourselves.