The landlord refused to lower the rent. So I notified her that I would be moving out in August. She told me that I would just owe her for the days I am there in August. I also fidgured she would charge me for the months the unit is empty. I have 2 more months on my lease. So I already have several names of people that want to rent the unit when I am out. I understand my landlord's frustration but I am not willing to pay her for back rent that has already been paid. I live in Las Vegas and she lives in Florida. She has never mailed me a receipt, but I have copies of my checks and bank statements showing the checks cleared.

So you have proof that she was paid up.
If the place is rented for Sept and Oct she can not charge you for those months.

That would be only Aug that you would owe her for.