You meet your friend in an event, you become close to her very easily as there is a natural connection. I know I had that. You get to know her to the core and the same with you. You love her as a sister, the same in return. The bond is natural and always a good healthy quality that every best friend should have.
Every so often, differences will show and cause arguments or open annoyance. However, sometimes a fight is so bad that you end the friendship. However, the natural bond on both sides shows how hard it is to separate and you reach out to her and she does the same when she is ready. You have an emotional conversation about the situation and exchange an apology. You feel like it's better to just be friends but the bond says no, you are meant to be best friends.
When you have a second chance, the bond is always stronger than the first. You realized that there is much more that is discovered in the second chance and you learn to adapt to the differences. You realize that you can relate so much more and can enjoy life so much better. Life is too short to hold grudges and not make the most with her.
Something every girl should understand that your best friend is always there and loves you no matter what. If you have a major fight, don't automatically think it's over, consider a break, and realize how much you miss her. My grandfather used to say "if a relationship is perfect, one person is dead". In that quote, he is stating it is not realistic to have a perfect relationship. There is no such thing as a perfect relationship. Speaking from personal experience, just remember what I said because of your relationship with your best friend is special and you should cherish it.