Owner Wants More Money After Confirmed Booking And Full Payment Made

Hello Trip advisor,I have booked a holiday rental accommodation and paid the full amount after receiving an email quote and confirmation to proceed with completing booking and payment made in full based on the rates available at time of booking quotation. Now the owner wants to charge more money because she said the rates at the time were set too low. She said that she will cancel my booking if I don't pay her more money, although I already paid the amount quoted by the owner in full with Trip advisor and receipt confirmation received. What do I do as she will cancel the booking if I don't agree to pay her more money. Please help I'm from Australia. Do you want to know the confirmation booking number and other information, please let me know ASAP.