I Need Some Advice, Dealing With My Fiance's Ex and Some of His Family! PLEASE HELP!?

My fiance and I have been together for five years, we have a two year old son together and we are getting married in august. Well my fiance also has a daughter whom is eight now and he has not seen her since she was one and a half. Well too make a long story short he tried to see his daughter for the longest time, but his ex would threaten him with the worst things possible. Then the Day AFTER our son was born she filed for child support againest him and the whole time I was pregnant she harassed me on the internet and talked badly about our son after he was born (I mean saying that our child was the biggest mistake in the world), But he pays the money to take care of his daughter. Well his ex has kept in contact with some of his family over the years and talks to them about twice a month, especially his aunt whom she calls a lot. Well when we called my fiance's aunt to tell her that she will be getting an invite to our wedding soon, she congratulated us but then started asking some strange questions about me like What is Gonna Happen to Her Disability? What Is Gonna Happen To Her Benefits From Her Disability? Basically she thought I was mentally handicapped psycho. Well his ex tells his family members horrible lies about me like she told them that I had a horrible disability and that I was getting disability and that I had some *issues*. Is there a way I can get his ex into trouble for any of this stuff? I really want it to stop and telling his family members not to listen didn't help us any? Please Help I really don't want to have to go through this for the next ten years.