While there does seem to be a shortage of female heroes in the comic book movies, there is Scarlett Johansson in the role of Black Widow. Scarlett reprises the role of Black Widow for Captain America: The Winter Soldier and she has opened up about the relationship between Black Widow and Captain America in the Marvel Cinematic Universe.

Scarlett Johansson as Black Widow
Johansson told Coming Soon, "Of course in 'Avengers' particularly you start to see the relationships forming between these characters, and all of us have very specific relationships with one another. Of course we all know how we feel about one another. We work and all use each other in different ways."
She added, "We all have very specific opinions about one another. I think that Joss laid the groundwork for a lot of interesting connections. That's why the audiences are so intrigued by that film because they love to see how these characters react to each other that come from completely different universes."

Chris Evans is back as Captain America
You can catch Scarlett Johansson, getting up close and personal with Chris Evans, in Captain America: The Winter Soldier, which opens on April 4, 2014 in the US, before then hitting the big screen in the UK on May 2, 2014.
Captain America: The Winter Soldier panel at Comic-Con