Translation:My aunt is smart, she is a teacher.
Sometimes "hen" is translated as "very," and at other times, it isn't. It's a drag having to memorize the exact couching of each "correct" answer, just to get through each lesson. Oh, well! I appreciate the fact that Duolingo has accepted about 40 of my suggested alternative answers so far...
That may be the most literal translation; however, one almost never says "maternal aunt" in English. In fact English simply has fewer words to describe family members so perfectly rendering the Chinese is impossible. Furthermore, 阿姨 is frequently used in China as a polite term of address for older women (your parents' age and up), whether they're related or not, so the word does not in fact always mean "maternal aunt".