She could look forward to around 300 years as one of the most politically powerful people in the world.
She had evidence that she could continue to push for a political solution to the Seanchan issue.
She knew if it came down to war, she was well set to give them a drubbing.
And her chief weakness, though she probably wasn't in a mental frame to admit it right then, her idiotic husband who would recklessly risk her life for no reason, was now gone.
She could devote herself to learning and growing the Tower. She had the most reason to want to live through the Last Battle.
She chose not to because the alternative was a new hole in the Pattern. She didn't kill herself to be able to follow Gawyn into the afterlife. It wasn't suicide, it was sacrifice.