^I don't get it lol
Also in terms of shipping, W doesn't have to forget about Theresa, people often have different partners in their lifetime. W can remember Theresa, while enjoying a relationship with someone like Amiya in the present.
Severa's entire character revolves heavily around her mother and her inferiority complex, to the point this might be more for a praise kink than anything
I assume you're not getting the Theresa'd Amiya pic? It just seems to be Amiya with Theresa's eye color and a white glyph in contrast with her usual black one. Notably, Theresa is associated with white.