Wow, there’s a lot going on in this thread. At the end of the day it’s a 9 going on 10 year old Accord that honestly is the perfect daily driver for the rust belt. I’d imagine this car will make it a solid 15 years before any rust presents a safety problem, possibly longer. They’re good cars, but nothing to get worked up about. I also get the sense that you want to blame your sister for the car’s condition, at least partly. If this car is causing resentment amongst family members either sell it or learn to live with it without resentment. I can just sense the resentment and frustration in your posts and it’s not worth it.
Me personally, I’d leave it the way it is and drive it until it has major mechanical issues, or until the rust poses safety risks. Good luck.