By mistake I added my mother in two places and I can't figure out how to delete the wrong entry.
If your mother is listed as living, then no one else can see the profile, and no one has made any changes. In that case, look at tools in the bottom right of the profile page, and "delete this person" will be available.
If your mother is deceased, and someone else has made changes, then the profile can no longer be deleted.
If that is the case, then you can use "Merge by ID" to convert the 2 profiles into 1.