I have gone in and updated Mary Nichols as a step mother but I cannot remove her from "my family tree". My great grandmother was Edna Linscomb.....totally different tree.
From your great grandfather's profile select the relationship you prefer. There is a radio button for that on each couple.
Is your great grandmother Edna Linscomb LKD8-WM6? It appears she has a duplicate profile GF19-WPB.
How to Correct Relationships
Correcting Mistakes in Family Tree