[Vigilanteman]

Before the journey, their travel agent informed Delta of Vilma’s condition and bought two tickets for her and one for Janos.

Sounds to me like the widower has good grounds for a lawsuit. 425 pound divided by two = 212.5 pounds or roughly the average weight of a middle aged adult. The airline not only breached a clear contract, but contributed to the woman's death by their refusal to fly her after she had followed guidelines and bought two tickets.

It wasn't some fatty trying to waltz into the aisle seat and hang her butt over the center at the last minute. It was a disabled person request which the airline was obliged to accommodate by being informed of the condition and selling the ticket.

[Procyon]

the flight attendants couldn’t get her out of the wheelchair and into the seats, even with the assistance of the local fire department. The airlines did the best they could do and offered them another route (she wasn’t in critical condition), but her husband decided to stop trying.

The airline didn't refuse to fly her. It appears they exhausted reasonable efforts and suggested an alternative which the husband refused.