Gandalf's niece

Somewhereve in Middle Earth there is a powerful Witch named, Einna [Eh-na]. She is the neice of Gandalf the Grey. She is the last witch in all of Middle Earth. When Gandalf requires her on a mission to Erebor with 12 dwarves and a hobbit, will she refuse or accept the offer? What if she falls in love? She has a secret she's afraid to tell. What will happen if anyone finds out?