Sister: a female person who has the same parents as another person
Soul Sister: Someone who fully understands you. Like a soulmate, but not someone you want to marry and make babies with. The sister of your soul.
2)Hayley just gets me, she understand everything about me, she's my soul sister.
2. That soul sister knows she's lookin good.
Girl #2 "Why don't you marry him then?"
Girl #1: "I would, but we're already soul sisters!"