She apparently went to the hospital afterwards, so they'll have the results of that testing. Though many times this evidence is really only evidence of sexual intercourse, so it's still he said/she said regarding consent without other evidence.
It's probably why she got the payoff, whether it was consensual or not. In Greasy Ron's shoes (assuming innocence, as that's a staple of democratic justice), a woman he had intercourse with (potentially rough, potentially intoxicated) has a lawyer dial him up and explain she's been the hospital and had a rape kit done and intends to press charges. He knows she has his DNA and there's no other evidence either way. The options are sign a check for what is in comparison $1-500 for you and me, or have her press charges which puts the story in the press damaging his reputation (which is what he makes the majority of his money on via endorsements) and risking conviction in a very circumstantial evidentiary trial.
To me the payoff is only proof of sexual contact. The fact that the sum is so low, comparative to Ron's net worth and income, leads me to believe she didn't have a very compelling case beyond the hospital exam that proved little. If she had good evidence to support rape, surely she presses for more considering Ron makes $100M+ in salary and endorsements per year?