I Know about You - Erin Kaste

Elementary school teacher Cary Smith thinks she has finally outrun her secrets. She's avoided attention all her life, but the moment beautiful Tina Flores joins the faculty, Cary wants to be noticed. Although the school has a zero-tolerance policy toward anything "immoral," Cary dares to pursue Tina, and they begin a relationship nobody can know about--not Cary's friends, co-workers, or ex-girlfriend.

But then strange things begin to happen, and before long, Cary isn't sure who she can trust. When someone begins leaving ominous messages and finally breaks into her apartment, Cary fears losing her job or even her life. With her stalker inching closer to the truth, she's forced to face the past she's tried desperately to forget.