Flight Attendant reported a passenger problem related to the passenger not wearing a mask.

Narrative

While B Flight Attendant did a second walk through the main cabin after the first beverage cart she noticed the passenger in seat; did not have her mask on. B Flight Attendant requested that she put her mask on. Passenger stated she was drinking her beer. B Flight Attendant informed passenger that she needed to put her mask up between bites and sips. Passenger pulled mask up after rolling her eyes. A few minutes later the passenger came to the back galley (with her mask down) to request a refund for her beer since 'she is not allowed to drink it'. At this time she did not bring an unopened can to the back. She was holding an open partially dented can. I did not refund the beer. I informed her she could finish her beer and put her mask up between sips. This is a policy that had been announced three times already during the flight. Passenger took her beer into the lav. Passenger asked for my business card. I did not have one. Passenger asked for my full name and I gave it to her with the flight number. When passenger came to the galley she had her mask down. I asked her to pull up her mask. And requested that she keep it on while talking with the crew. She pulled it up. This passenger felt my request was unreasonable. She will be writing in to complain about me. I reiterated that the mask policy is a federal regulation. This passenger was wearing a gator instead of a mask.