Living vs Death Accounts
Answers
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If your mother is deceased, then the first step you need to do is to go to the living profile for her and change her death vital event from Living to Deceased (filling in what you know about the date and place of death).
Then you should be able to merge that profile with the other profile that is already marked as Deceased.
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Only you (the person who entered it) can see the profile that's marked "living", and no, you cannot merge the living with the dead on FS. (Apparently you can, over on WikiTree, and fixing the resulting mess is ...Great Fun.)
It appears that the correct status is "deceased", and Alan already explained how to fix this. For future reference, if you ever encounter the opposite situation, i.e. a public ("deceased") profile for someone who's alive, here's a Help Center article on changing the profile to private: https://www.familysearch.org/en/help/helpcenter/article/how-do-i-change-the-status-from-deceased-to-living-in-family-tree.
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