I had a similar thing happen to me with a woman on a LUS 321 a few years ago - asked if I could move my backpack, my only carryon item, which was too large to fit under the seat, ten rows back so she could fit her rollaboard. I politely said no, and then she responded very loud and sarcastically, “Thank you for being reasonable!” And I politely said “You’re welcome!” And she went on and on about what a jerk I was and I ignored her.