Hair

Hair is a person's history

Cutting hair is a way of moving on from the past

Braids could possibly be using history as strength.

When Mrs. Shepherd came into town, Izzie put Meredith's hair in a high and uncharacteristic pony tail. Meredith, during this time was disguising her history. It is only when she takes her hair down that she shows who she truly is to Mrs. Shepherd.