Xita (The Lovely Letters Book 3 Second Edition) - The Lovely Letters, #3

Xita picks up where Kassie left off. Leander - the Alpha leader of the Golden Pride is determined to do whatever it takes to find a cure for the toxin that is incapacitating his people. This leads him to enlisting the help of one of the top minds in the laboratory designed and built specifically with shifter care in mind. When he introduces his new employee to the Vampire Prince, Avalon he discovers the she is another of the "witches" they have been searching for.
Fearing she won't be able focus on solving this problem if she learns the truth, Leander decides to keep her in the dark of what she is.  What he didn't see coming... Xita Stuart - A brilliant red haired, green eyed scientist who can't say no to a complex problem, or the tall blonde haired man who makes her mind stray out of the lab and into the bedroom. Of course she'll just have to work harder at keeping her thoughts in order since he is also her boss.
Easily done as long as she can keep her focus on uncovering the truth. As a methodical creature, Xita takes certain steps that inadvertantly reveal more than the toxins she's researching. Neither Leander or Xita could have predicted where those truths would take them. This is the 3rd book in the Lovely Letter series. It is a continuing series and all books are meant to be read in order.