She comes from an advanced civilization. In 3x06 she claims she was doing Calculus at age 4, and that the science classes at Midvale High are too easy. In the comics, Kara Zor-El is a super-genius like her cousin.
Yet throughout the run of the show, Kara leans on Alex and Winn for her science, J'onn for tactics, and James for wisdom. She mocks Alex at one point for studying "molecular blah-blah". Max Lord calls her "muscles" at one point, plainly dismissing her intelligence. Sure, she does flash smarts every once in awhile, but seldomly.
Seems like inconsistent characterization.