One or two??

This is a story about two best friends Diana and Sunny. Two poles of the same axis. Sweet, salty. Calm, short tempered. Rational, stubborn. Lively, gloomy. One cries - other wipes her tears. One frowns - other makes her smile. One looses hope - other shows her the sun. One pains - other soothes. One shrivels - other blossoms. But then just as the poles have a single center of gravity, so do they.. two different personalities.. one life. One her!