Hi Coen Veldhuis, when you connect a Firefox installation to a Firefox Account, the contents of the account are synchronized between the various installations of Firefox you have connected to the account. Disconnecting from the account does not clear the locally stored data.

Are the account mixed up, or is there no separation between different usernames and passwords on the same computer?

If you have different Windows logins, each login should have a distinct set of profiles -- settings folders. If you open the about:profiles page (type or paste about:profiles in the address bar and press Enter to open it), do you see the same list whether you are logged in as yourself or as your wife?

Quote: After i logged out from my own account

What account do you mean ?

If this is about the Firefox Account you use for Sync then connecting to a different Firefox Account in the same Firefox profile folder will mix up data stored on the Sync server and your wife can see your passwords if she logs in to that same account. You should never login to more than one Firefox Account for Sync in a Firefox profile unless you intend to merge data.