What can I do if my fiancé was accused of first degree rape by his daughter's friend?

She claims this happened back in 2013 on two different dates. She did not report it until 2015, no rape kit, no nothing. It is her word against his. She was supposedly 15 or 16 at the time of the incident. There was never a protective order or restraining order filed. On March 31, 2016, he got arrested at our home and never read him his rights or showed him a warrant nor did they tell him what he was being arrested for until they put him in jail. We do believe that the child's mother had something to do with this because she tried to hook up with my fiancé and he told her no because she was married at that time and still is to this day. Her husband is actually in the middle of divorcing her as I type this. She has filed so many protective orders against other guys and people. It’s just not funny. She is crazy. How can we get this dismissed without any evidence? We have 2 witnesses that can verify where he was on those dates but that is it. Also, can we file charges against her and/or her mother for false accusation, time off work, missing out on pay, attorney fees and court cost?