if you had a local offline account when signing into her Xbox/Microsoft account, chances are you accidentally clicked through the option that asks if you want to sign into ALL things on the computer using that account rather than just isolating to the Xbox app and maybe MS Store only.
In the event you did this, (which it sounds like you did) that account got signed into and linked to ALL Microsoft related things on the computer, from the user account, to the MS Store, to Edge.
(also, if her account was set to sync, then after signing into it on the MS Store, that probably is what started it all. You should've just logged in from inside the Xbox App not the store.)
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In regards to your browser history and settings, if you had any login info for certain websites saved, it might have gotten synced with her account.
If this happened, you can simply open the browser, go to it's saved logins/password section, and search out all your login stuff and delete the saved info after that delete any bookmarks that are yours, then sync the browser data, then log out of her account on the browser, after which you can also go and log out of her account on everything else in the computer (not sure if you can unlink a Microsoft account from a user account after it's been linked, but I'm sure you can Google how, as there might be a way)
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After you've scrubbed your data from her account on the browser, and scrubbed her account from other things in the system, I highly recommend you do as someone mentioned and instead, create a new user on the computer, then log into the account with that second user so that it's isolated from your main user account on the PC. This means that you have to switch user accounts to be able to play games, but that shouldn't be too much trouble imo.