ex-wife harresses and makes false statements

A friend of mine is seprated from his wife and she is always harrassing and making false charges(examples:sexual abuse on his 2yr old daughter, child abuse on his 5yr son, stalking her, kidnapping) none of these were founded or he has not been charged with any of these and all claims were dismissed! When the police show up they say that they know she is lying and there is nothing they can do and state that it is their job to deal with liers on a daily bases. Can't the police charge her with false statements? He would like to take her to small claims court but unsure of what kind of charges he can sue her for.