Why She Will Be Nominated: She should have been nominated last year! Edie Falco gets all the attention for Nurse Jackie (rightfully so), but Weaver is the most underrated actress on that show. She lights up every scene she's in.
Why She Won't Be: "Underrated" is another term for "an actor that will be overlooked come Emmy time for no reason other than they are not a well known name." And it definitely applies to this situation.