"She does not study hard."
Translation:그녀는 열심히 공부하지 않아요.
From what I gather, 지 at the end of one verb stem before another verb is just a way of bridging the two together. :) If the next verb begins with 마, then yes, but if it begins with something else, 마 won't go there.
만지지 마세요. "Don't touch." Would be an example of the next verb starting with 마.
I hope that helps!