Dear LIB readers; my ex is stalking my wife

From a male LIB reader

I got married on February 7th 2015 to a girl I met and fell in love with in 2014 but ever since our marriage my ex-girlfriend has been harassing my wife with text messages, emails and on Facebook, telling her things about my past. She doesn't come as herself but I know it's her because of the information she passes on to my wife. We broke up about a year ago but she has refused to leave my life alone. She's trying to turn my wife against me with lies. I called her the other day to ask her to stop contacting my wife but she feigned ignorance and swore she is not the one. But I know it's her, no one else has a bone to pick with me. How do I get her to stop before she ruins my marriage?