You was Bella swan's younger sister, Charlie and Renee's youngest daughter. When Bella decided to move down to Forks to live with your dad, you went with, so your mom could travel with step-father, Phil.
After a few weeks of living in forks with your dad, Bella got curious and ended up finding out the Cullen's secret of them being vampires, she had told you all her suspicions and then told you after she found out.
It was a complete shit show, the problems that came with Bella being Edward's mate was a mess. Then Edward had let slip that you was Emmett's and Rosalie's mate as well, which caused a mess, Edward knew why the couple didn't tell you. One you was younger than Bella, and two they hadn't known how you would've reacted.
It took a few weeks, but you warmed up to them and it kind of all fell into place, the couple had been together for ninety years, since they were turned, and while you were human, and younger in human terms, they really did love you.
Now just over a year later, Rosalie was sat scowling at you and Emmett, trying to hide her amusement as she watched you and Emmett messing around, you clinging to his back, and him running round like a lunatic. Rosalie also found it amusing that you was dead set on blasting 'Get Low' from the speakers in the living room. Which, consequently drove the rest of the vampires in the house mad, but they didn't say anything against it, knowing how sassy Rosalie would get at them.
"You'll drop them if you continue Emmett." Rosalie said, trying her hardest to bite back the grin that threatened to tug at her lips.