Infinite Days (Vampire Queen) by Rebecca Maizel
Many of us wonder what it would be like to be a vampire....but how many vampires strike to be like us? Lenah has been a vampire for hundreds of year, but she yearns to return to her human life. Rhode - a vampire willing to die for Lenah to have her wish - succeeds in returning her to a mortal life in today's world.
But mortal life is not what she expected. She is enrolled in an exclusive high school and must adapt to life in a new era. As she makes new friends and finds a new life, she must be careful not to let her past catch up to her...because it is hunting her, and everything she has grown to love could be destroyed if it catches up.