Except for Millaine, all girls that betrothed with Leon have their own 'big' arc. Clarice and Deidre don't have that (yet), most likely wont.
The author treats Clarice like a tragic side character, and she doesn't seem to be promoted as heroine (yet), plus as long as Leon's brother will end up with Deidre's sister, I think their father will give up matchmaking Leon with his daughter. Still, the author treats Deidre like a teasing-oneesan side character, unlike what he does to Louise.