All you need to do is click the edit tab on Lois' profile and where it says "add Mother" click on that and a page will open.
At the top it will say;
A.) If the mother has an existing WikiTree profile enter the WikiTree ID here:
You just add her mother's ID (in this case Grant-12015) in the box provided and press GO.
She should appear automatically.
To get Lois to appear as Lois Fotheringham, remove Hay as current last name and replace it with Fotheringham. Then you can remove Fotheringham from the Other Last Names field.