I inadvertently triggered a swipe up gesture on my Android phone yesterday and discovered that swiping up/down on your little avatar in the upper right of Google apps (e.g. GMail, GDrive, Play) changes the Google account you're looking at. #littlethings #whytaptwicewhenyoucanswipe4times #actuallynevermind
Chrome has some sort of little prompt that pops up and if you click okay to dismiss it, changes the default user associated with that Chrome instance.
My wife is "Person 1" on Chrome on her laptop. It *really* wanted her to be one of her various Google accounts (including her old nursing school account).
She clicked "OK" one time and, from her perspective, everything changed and she thought she'd lost all her bookmarks and open tabs.