$150 isn’t enough to get her off the tarmac. The airlines do cram everyone in like cattle in a box car. It’s awkward and uncomfortable for everyone regardless of size, and nastiness toward larger folks only makes the experience worse.
My worst “personal space violation” experience didn’t involve a heavy person, but a straight-sized woman who crawled across me in my aisle seat to get to her inner seat without any warning or giving me a chance to stand up and let her by. I hadn’t my caught my breath from this jarring violation of my personal space when her adult (also straight sized) son did the same thing! Who TF thinks it’s okay to crawl over a stranger? They tried it again when they needed to use the bathroom and I had to shout “Ahh! Ahh! Ahh! at them like they were unruly dogs to stop them while I stood up.
I’ve sat next to plenty of plus size passengers over the years and they’ve always been far more respectful of personal space than those lap-crawling cretins were.