Graphic novels suitable for a preteen with badass female characters

[Shippou-Sensei]

I'll note Sailor Moon is on there. I saw someone pooh-pooh it earlier in the thread, but really despite the rainbow-coloured cutesy vibe, it's hugely influential and much loved by many feminists as a great, strong example of girls being fucking awesome on their own, forming strong friendships, and all the usual good stuff.

It really does start off as dubious monster of the week stuff.
From what I know or at least suspect is that things started to change as the number of core characters increased and it was more about interactions of the characters than the plot.

Also to start with sailor moon gets saved every week by a guy. Tuxedo kamen.

Also a lot of this may apply more to the tv show than the manga. The manga is only 15 volumes where there are like 200 tv episodes.

 

[Shippou-Sensei]

For an intresting flip on the mahou shoujo series try the anime madoka. It takes a large number of the tropes from traditional mahou shoujo series and then twists everything around.
Brutal series with lots of gut punches but well worth watching.

 

[Shippou-Sensei]

Also as I said before if I was going to pick a series to start on for mahou shoujo it would be a clamp one. Probably card captor sakura. but magic knight rayearth is really good too.

 

[Vintage Paw]

I recently watched Monthly Girls Nozaki-kun. It was really good fun. It's not overtly feminist with kick ass girls kicking ass, but it subverts the types of roles you usually see. Of the main female characters, they're all interesting, and don't all fit into a typical mould. One is distinctly androgynous (indeed, her gender is often up in the air), another is feared by the entire boys' basketball team because she's mildly insane and beats them at everything. The male characters don't fit traditional roles either. There's one particularly funny episode, where 2 of the (presumably straight) boys sit down to play a dating game. The kind where there are several girls to choose from, etc. By the end of it they've become utterly entranced by the male character in it, and sit up all night furiously writing yaoi

The lead female character, Sakura, is equal in terms of her competence (the premise is they create manga together, and she's as integral a part of the team as the rest of them). And she's hilarious. And rather melodramatic, in a great way.

I mean, it might not at all fit the bill in terms of the OP, but gosh it's really great fun.