User blog comment:Living Machine/Marvel Movies Ideas/@comment-2198188-20130223063054/@comment-3317214-20130224143949

Casting reasons. If we're talking about her getting a solo movie, then the director/writers of that movie (which wouldn't appear until at least 2016) would be stuck with whatever casting choice some other director makes when considering actresses for a random supporting role in a sequel to Iron Man, Thor, Cap, Avengers, or the Guardians film.

Also, we pretty much know she's not in IM3 or T:TDW. And CA:TWS seems fairly crowded already with Falcon, Black Widow, Nick Fury, Maria Hill, etc. And I don't think GotG is the place to introduce her either. And Avengers 2 needs all the time it can get to focus on its main cast.