Thank you all, I'm so upset about this. She didn't leave early, she stayed the two nights she booked. She messaged me yesterday with a list of issues she had, including: not enough towels, and the power went out in the middle of the night. I live on property, in the back unit of the duplex, and I spoke to them during their stay twice and they never asked for more towels. They had 6 in their group and there's 10 towels in the unit. The power outage is out of my hands, the whole street was out.
Her big threat was over some friends we let park in our driveway for a big beach festival down the street. apparently they were loud and yes, from drinking, when they came back to get their cars at midnight. I know this was a mistake, and I'll never have friends over again because of this. Our friends all said they did yell to one another about who was going in who's car, but after one minute they got in the cars and left. This guest is claiming there was an escalating altercation on my front lawn and she thought of calling the police! She's also claiming her group pulled up as our friends were outside, and that's not true either. She knows we weren't there to witness any of this and she can say whatever she wants and I can't really argue.
I understand that this was a HUGE mistake on my part letting festival goers park at my place, and I'll never do it again. I feel extorted on the other hand, specifically since she directly threatened to post the awful review if I didn't refund.
I am going to give her a refund for that night, because I feel terrible she's not totally happy, and I'm worried if she knows I changed my review, she'll go back on her word and post the bad review even after I refund her.