I Won't Give Up My Window Seat on a 10-Hour Flight

I booked a window seat on a 10-hour international flight months in advance. A woman named Helen asked me to swap so she could sit next to her husband. Her seat was a middle seat four rows back. I said no, I planned this trip carefully and I get claustrophobic in middle seats. Helen said "it's a long flight, please, we're married." I said I'm sorry but I specifically chose this seat. She got the flight attendant, who said seat swaps are voluntary. Helen spent the first two hours giving me dirty looks. Her husband came by once to ask again. I held firm. The couple across the aisle told me I was "technically right" but "not very kind." I paid for this seat. Am I really the bad guy for sitting in the seat I selected?