Action Heroines are badasses who are female. They can fight their male friends without breaking a sweat, avoid being kidnapped, they break themselves out of trouble when int trouble. These girls can prove, with her very being, that girls aren't only not helpless and not so harmless, they kick ass and can be quite dangerous to their foes. These girls routinely and reliably gets in on the combat. And what's more, she wins.
Sometimes girls become this if they toughten up, get in fights and win, avoid being helpless, So any girl can be this but not all girls are this. Twilight Sparkle, Bubbles, Starfire and Sari are those are this type by default and Lizbeth is a example of someone becoming one through character development and resolution.