I was on a United flight this am and seated next to me was the passenger from hell. She was in one of the late boarding groups and complained when she boarded because overhead space was at a premium even though the GA had advised of this before boarding. Then she proceeded to take her seat in the middle. The entire flight she made snide comments to the gentleman seated in window seat. As the flight was descending she asked the FACT for information on sending complaint to United regarding gentleman seated at window. She then advised the FA that she was a "secret flyer." United doesn't get enough complaints from paying customers that they have to pay people to complain? Anyone else heard of this?