Girls and boys equally consumed a lot of comics when I was a kid (back in the 1960s) and you can see that there were several super-hero comics that would have appealed to girls.
Wonder Woman was probably such a success in the 1940s because she was a character that boys, girls, men and women all equally enjoyed--likewise with the original Captain Marvel, whose comics sold in the millions and appealed to the whole family.
In the 1960s, it's pretty clear that both boys and girls were reading about Supergirl and Lois Lane. And the Legion of Super-Heroes is noted for being a team that had great appeal for female readers--as that team had so many strong female characters.
Beyond super-heroes, of course, there were lots of other kinds of comics in the 1960s. So girls were looking at the spinner racks and buying Archie, Harvey, Dell and Gold Key comics. And sampling stuff from DC and Marvel--mostly romance, Sugar & Spike and teen humour, but they were more likely to discover a super-hero or two also.
What happened in the 1970s is that sales declined and, as comics moved into the comic shops with lower print runs, Marvel and DC targeted those who were most likely to be in the comic shops--which were teen and young adult males looking for male super-hero comics. And the women in those comics also tended to be male fantasies, without many qualities that women could appreciate.