Am I the a**hole for not leaving my seat on the airplane to let someone with a disability sit?

I'm not really sure if this is a good place to ask, so I'll just let the internet decide. <br><br>I was traveling home for the holidays and got on a plane. The person sitting next to me at my window seat got up to use the bathroom and the lady sitting across the aisle from me called me over and asked if she could sit in my seat because her butt hurt from sitting for so long, which made standing almost unbearable.<br><br>I politely said no, as I would like to look out the window during the flight and I don't want to get up every time I want to look out, as the person next to me did that a lot and it was annoying.<br><br>The lady sat pointing telling me to let her sit because she has a disability that prevents her from sitting properly and standing for long periods of time. I told her I'm sorry but I really don't want to let her sit, mainly because I was looking forward to not having the person next to me get up every 5 minutes.<br><br>She then said it wasn't nice of me and I was an asshole for not letting her sit. I felt bad for her but didn't really want to give up my window seat. Am I the a**hole?