A chainsaw-wielding cheerleader with a human head strapped to her belt may sound an ambiguous role model but at Comic-Con, the pop culture expo, that counts as feminist progress.

Juliet Starling, a high-school zombie hunter, is the lead character in new video game Lollipop Chainsaw and the latest sign that the annual US jamboree of graphic novels, television shows, Hollywood films and digital spin-offs is embracing strong female roles.

A trade show once famous for a male-dominated mix of nerdiness and casual sexism wrapped up its five-day gathering on Sunday with more female presence – fictional and real – than ever before. Some 40% of the 130,000 visitors who packed San Diego's vast convention centre were girls and women, thought to be the highest proportion in the event's four-decade history, and there were robust female characters on page and screen.

Many were "Twihards", fans of the Twilight vampire saga who camped outside the convention centre for days to see a panel discussion with cast and crew members. Others came in hope of meeting EL James, who was signing copies of Fifty Shades of Grey.

"Comic-Con is evolving. It's not as male-dominated as before," says Clare Kramer, the actor who plays Glory in the TV series Buffy the Vampire Slayer. "Look around, you can see it's women-friendly." Kramer was there to promote geeknation.com, a new entertainment site she co-founded. The term no longer belonged to adolescent boys, she said. "Geek is now all-encompassing."

Strong female leads are not new. Princess Leia started zapping stormtroopers in 1977 and Lara Croft swung into action in 1996. But in recent years the number of female heroes has grown sharply, says Josie Lee, a pinup model and actor who did the body mapping for the character Delta in Bio Freaks.

"There's the same violence and cleavage as before but now women can be the main hero and that's encouraging female participation. Just look at all the girls here dressed up as Lollipop Chainsaw." There were, indeed, numerous girls and young women walking around with a variety of weapons, fake blood and cheerleader outfits. "It's slow progress but it is progress," says Lee.

Not everyone agrees. Troy Stiegerwald, 28, a photography student from Denver who wore a mask from the web horror series Marble Hornets, welcomes female characters who "kick ass" but questioned why so many did so in skimpy outfits. "The men wear armour that would genuinely protect them whereas the women wear armour that reveals their sexual assets. There is still a lot of sexism in this industry."

Comic books and posters that combined Baywatch with chainmail, or had warrior princesses doing interesting things with pythons, illustrated her point. Some companies also employed "booth babes" in revealing costumes to attract punters.

Alex Buechel, 31, an illustrator from Michigan who specialises in erotic pin-ups, says his work is not sexist. "I just think it's beautiful, and so do a lot of women." Many male characters, such as those in the graphic novel and film 300, bared flesh, he adds. "The guys were almost all naked. Everyone knows sex will always sell."