The Hobbit: The Desolation of Smaug actress Evangeline Lilly is currently in talks for the female lead opposite of Paul Rudd in Marvel's Ant-Man.
According to The Hollywood Reporter, the talks are only early and it isn't clear who the former Lost actress would play in the film. The site does note that it likely would be a decently large role as it appears it wouldn't be a one-time role.
If she does sign on for the Marvel superhero film she will join the already cast Rudd, who is playing the film lead as Scott Lang, while veteran actor Michael Douglas is in place Wikimedia Commons