Definitely fell way too far down the rabbit hole on this one, but I decided to read the court filing. From what I can tell, the evidence is basically those emails, her telling a number of people, and a polygraph test.
She never went to the police, and given the evidence presented in the filing, it's unlikely they'd be able to convict anyway.
I'm fairly certain that polygraphs aren't admissible in court, unless both sides agree, which they wouldn't in this case. I'm sure both sides would have witnesses, so it would come down to who's more believable. Seems to me the emails are key.
Her story is certainly compelling, but it's just one side. Based on Brown's lawyer's statement, it sounds like they have evidence of her asking for money from him in the past, which wouldn't be a great look for her. I would bet it will depend on how good each side was at keeping all communication between the two.