To be honest, I am trying to get my arms around how the buyout on that lease is $24,000. I'm guessing her lease payment is about $279 and assuming she has an Accord. Looking back 3 years......which is when we were looking at Accords and ended up buying a Camry, it was in the midst of the pandemic, before the chip shortage and dealerships was wall to wall cars and that is about what that car should have sold for new. They were dying for customers $279 a month times 36 months, she has paid $10,000 on that car. Her lease buyout should be in the $15-$20,000 range, not 24,000.
First thing I would say is NEVER go to the dealer that she leased the car from. She got ripped off. She can get a new Civic for the buyout on that lease. If that buy out wasn't so out of line, I would say buy the car she has now. She needs to negotiate a fair, and lower price on a new Civic and keep it the rest of her life.
I have never been a fan of leasing. I faced the car buying decision with my mom when she was 80. The 27 year old Pinto she bought new developed an engine problem. It only had 77,000 miles on it, but she got her money's worth. She was actually upset because she figured that would be her last car. I told her I was sorry she outlived her car. It was a chance for her to get that Cadillac she always wanted. But she said "I went to the Ford dealer and bought the least expensive model they sold, that is what I am going to do again. If it lasts 27 years, I will be 107 before I need another car". She lived another 10 years, put 10,000 miles on the new Ford Focus she bought. I sold it (to my future daughter in law) when she passed. No big deal, since I turned 18 I have always been joint owner of my mom's cars.
If you are concerned about getting rid of a leased car if she passes during the lease term, owning it would simplify that situation. Sell it and pay off the loan balance.
I really thing the decision to lease has not been a wise financial decision for your mom.