So there is this guy who has been envyed by his cousin since they were kids and now she is accusing him of....?

harment and touching one of her children. she has almost ended this guys marriage, got a restraining order against him, had him homeless at one point and is now trying to turn all of his friends and family against him behind this lie. What should he do? can he sue her for harment, false accusation or name slandering?