@Tina8345 I don't understand your listing- the first one is the only one I looked at (to see if you had mentioned slow wifi). You have almost no info about the accommodation itself, and you have it listed for 9 guests, yet you have no photos of all the bedrooms. Where are 9 people supposed to sit down to eat together? I don't see a dining table, just some counter seating and a bistro table for 2. Nor is there seating for 9 in the living room. Theere is seating there for 4. And what's with the empty room photo?
I see that you do mention the slow wifi in the description. If that wording was there when this person booked, I wouldn't offer any refund at all- guests don't get to leave and assume they will get a refund for something that was clearly mentioned in the listing.
It sounds like this guest is a refund scammer. She should pay what you charge per night if she only stayed 6 nights, not some pro-rated amount based on the monthly rate.
And don't refund her anything for nights you are unable to rebook.