There doesn’t need to be a judicial resolution of it. The solution is clear on its face. You move the woman to another seat; have her switch with some MMA type strong dude flying alone. If nothing else happens, great. If MMA dude says that the guy is wanking it, you now have two people and the woman is believed. If the woman complains that a second guy is wanking it, maybe you then think that she was making it up.