Is it possible you had the "Edit your details" page open and your web-browser "helpfully" auto-filled the form with her details and you submitted the form without noticing?
It gets worse: there's a lot of web-apps out there (both SSRs and SPAs) with <form> elements for personal details which are in the DOM, but "hidden" by doing tricks like `position: absolute; left: -99999px` inside a div with `overflow: hidden` (instead of doing something like `display: none;`) - or have the form hidden by using a z-index behind some curtain/cover element - and I've seen browsers auto-fill those fields and they get POSTed and cause a data overwrite on the server without the user being aware.
It's a fun way to steal PII from people: have a random public webpage that contains a registration form with all kinds of personal details, but has HTML+CSS such that it's visually obscured from the user, but the browser thinks it's a fully visible form, and simply yet the browser autofill it and submit it using JS (getting around the "user must interact with the page" filter by binding it to a big pink button that says "click here to see dancing bunnies!").
Browser auto-fill is dangerous.