23. You Buy Each Other Things Just Because
You and your best friend will always be thinking about one another so when you're out shopping (with or without her) and you spot something she'll like, you have no choice but to buy it for her. The idea of her happiness is all the reward necessary. You also don't mind going without that pair of shoes to surprise her with the necklace that you know she'll love. Besides, you'll probably get to borrow it at some point when you're exchanging clothes so it's a win-win situation.