Reunited

First book.
Vanessa Salvatore, 164 year old vampire. Twin sister of Stefan and younger sister of Damon. Through the first 64 years of her vampire life she found her soulmate in the youngest Mikaelson brother, and became best friends with the ruthless Niklaus Mikaelson.

What will happen when she returns to Mystic Falls?
When Klaus comes for Elena. will she help him or save Elena?
How would her brother's react?

It links with some of TVD.