Considering both Rhea's and Edelgard's backstory this does sort of make sense. Although given Edelgard's anti-church and crest mindset it might be hard to convince both her and Rhea to get along. Although if anyone can do it it would probably be Byleth.
I didn't think of it till you mentioned it, but now when I look at this picture I'm imagining Ingrid as a yandere not wanting her Bernadetta to be with anyone else.