This question may have already been asked... I made an attempt to find it and was unable.
Yesterday, I ran the most recent HighSierra update on my Late 2009 iMac. This computer has three separate user accounts, I am the only one who has an AppleID and I am also the admin. My mother was the one who initiated the update; from her user account on said computer.
When the updates were finished, she was the first to try and use the computer, being that she does not have an AppleID or admin privileges, I came over and did the seemingly usual sign-in process. However, I was unwittingly signing my iCloud and all that goes with it into her user.
I do not want all those things signed into her user, because she now has access to my iMessages, my emails and other things. As a temporary fix, I went into her Mail app and edited my iCloud mail setting so that that would not be coming into her inbox, I also went into System Preferences and turned off most of the iCloud services (contact syncing, notes etc).
However, the above was just a temporary fix, how do I get this reset so that my iCloud is only signed into my user and my mother does not have access to my emails and such?