Defamation: Accusation of Molestation

My question involves defamation in the state of: Arkansas

I have a question and my family really would like some answers in clearing up a very sticky situation.
A year and a half ago my fiancee and his ex wife divorced. As a condition of the divorce, my fiancee had to take a DNA test because the couple had a daughter together. Well it turns out that he was not the father of the little girl. As soon as the DNA results came back and the divorce was finalized, his ex wife started saying that my fiancee's father molested and raped the little girl. Police reports were made but the child went to four hospitals with no evidence of any sexual abuse found by doctors. My soon to be father in law was never arrested, never convicted and has never been legally approached of this matter.

Things settled down over the next year and a half (this apparently happened in April of 2007) without a word about it. A few days ago my fiancee and I settled on a wedding date. His ex wife found out and has been trying to "win him back" or so she thinks. She'd started emailing him and acting all chatty and flirty, but at the same time,she has been harassing me over the internet and being really childish by calling me names, talking about my weight and my appearance. I am not obese or even fat but she's posting blogs about me on MySpace. She'll tell people to go look at my profile to see how "ugly" I am. I've done the grown up thing and ignored her. My fiancee emailed her and told her to leave us alone she'd done her damage and he didn't ever want her back. He told her that as far as he was concerned, she didn't exist. Well that made her mad. Now she's attacking his father again by throwing up these molestation/rape charges once again. She's posting on the internet (myspace) that he is a rapist and a molester. She's telling alot of people this either by posting blogs on the internet and by her own mouth. But see, he was never convicted or even arrested for that matter. He never even went to court. Isn't this called....slander? Can't my soon to be father in law sue the socks off her??? And she has posted copies of the police reports on the internet and isn't that illegal itself? And she's also naming four other different so called victims.

But the funny thing is...she has been sending my soon to be in laws updates on both of her children (she has another little girl from another fling) Such as, how they're doing in school and stuff like that. She's real friendly with my in laws sometimes. She sends them pictures of the girls. Now think real hard...if someone apparently raped your daughter....would you be sending them pictures of her? Would you send the accused rapist updates on school grades/illness/ect??? She doesn't sound like the mother of a molested girl. If something happened to my child, I'd be proactive about getting the abuser in jail and not beat around the bush for nearly two years and threaten and slenderize. I'm positive my father in law is innocent on these charges.

She has also accused every male in a five mile radius of her house of touching her daughter, even the grandfather (who IS dead and in an urn! So there's NO WAY the grandfather could have raped the girl!) Can this crying wolf so often give her discreditability? The woman has history of meth and even went to the police station to fill out a police report on my father in law high. The cop had stopped taking notes on her case and began to take notes on her!

And the last thing is that she accused this almost a year and a half ago. Is there a statute of limitations to when someone accuses another of something and doesn't do something about it? Because she'll raise a ruckus for about a month or so and then shut up for awhile. I kinda feel bad because all this started up when she found out how serious our relationship was and that we are getting married. I know I shouldn't think it my fault that she's causing his family hell, but partially I do. All this started back up when I came along. I wish there was something a person could do about jealous, childish exes. The world would be a better place if some people would just grow up.