Walked out of my sister's wedding planning meeting and I need a verdict

My sister asked me to be her maid of honor back in January, and I said yes before I knew what I was signing up for. Fast forward to last Saturday at my parents' kitchen table in Columbus, we were supposed to finalize the seating chart, and she handed me a 14 page spreadsheet with color coded tabs. I told her I needed to step back from planning duties because between my job and her weekly 2 hour calls, I was running on 4 hours of sleep. She called me selfish in front of our mom and said I was ruining her day. I still plan on showing up to the wedding in June with a gift, but I handed the binder back to her that night. Am I the jerk here, or was that spreadsheet a sign to bail?