Exiled Heiress: My Island Stockpile

Tara Sterling is swept away by a tsunami, traveling interdimensionally to Desolation Isle as a fake noble heiress. Using her Private Island Dimension, medical skills, and combat prowess, she fights back and befriends Garrison Commander Cedric Shen. They battle bandits, uncover conspiracies, and quell rebellions. She builds Peach Haven Island, becoming Island Lord; he ascends throne as emperor, abdicates to live in Peach Haven. The pair stay together, enjoying a prosperous, peaceful life.