In her 25 years of marriage to Jeff Bezos, MacKenzie Bezos has been a loyal ambassador for Amazon, the company that made her and her husband the richest couple in the world.

Ms. Bezos, 48, is a novelist. But Amazon has defined her public image almost wholly. The announcement this week that she and her husband would be getting a divorce may soon change that. A statement signed “Jeff & MacKenzie,” which was first posted to Mr. Bezos’s Twitter account, read: “After a period of loving exploration and trial separation, we have decided to divorce and continue our shared lives as friends.”

She was an integral part of its origin story, driving to Seattle in 1994 while Mr. Bezos sat in the passenger seat, working on the nascent company’s business plan. She was Amazon’s first accountant and was involved in its transformation from a small online bookseller to the e-commerce behemoth it is today, the second company in American history to be valued at over …