Sansa Stark
Snowflake
She loves snow and she loves you
Arya Stark
Love
She called you this because she loves you
Daenerys Targaryen
Darling
It was simple but effective
Margaery Tyrell
Y/f/f (your favorite flower)
You always thought y/f/f was gorgeous and she thought you were gorgeous. So she called you her y/f/f.