The question of how to attract female readers to comic books is the source of much debate and hand-wringing in the industry. The major publishers both, on occasion, decide that they're going to make an effort to get girls into comics. They know that girls like manga, so they try incorporating anime/manga styles and tropes (e.g. Marvel Mangaverse, which is generally terrible, and Mary Jane, formerly Mary Jane Loves Spider-Man, which is charming and fun). They push titles with female heroes beating up baddies. They succeed marginally if at all.
I think the problem is not necessarily one of methodology (although those attempts at anime-fying superheroes can be pretty hamfisted), but of scope. When a publisher decides to attempt to woo female audiences, it's usually its own little thing, set apart from the rest, like one or two titles devoted to the purpose. Meanwhile, the rest of the editors, writers, and artists continue to operate under the (safe) assumption that their audience is primarily young men, and produce accordingly. They know their audience; it just isn't the audience they want to add. So the peace offerings to the female contingent drown in a sea of testosterone, and as a result female readers don't get a significantly better impression of American comic books as a whole.
People tend to repeat the assertion that the problem is that many male writers attempting to write "strong female characters" end up writing macho men with breasts. To some extent this is true, but they also point to the "bad girl" comics as examples. This is a red herring, I think. While "bad girl" creators were fond of claiming that they were promoting "images of strong females", this was never more than an excuse. The central premise behind the bad girls, which I'm certain all of those writers understood, was to have a adolescent wank-fantasies for protagonists, while giving them "macho badass" personalities their adolescent male readers could grok (many boys would have a hard time letting themselves identify with a character who worries about her appearance or is otherwise "girly", but punching people in the face is much more in their comfort zone).