Seppel is best known for her prose for children's books and her poetry. In addition, she has appeared as a lyric translator from various Turkic languages (Turkish, Azerbaijani, Uzbek, Kazakh, Tatar and Turkmen), Russian and Finnish. With her husband, she translated a selection of stories from One Thousand and One Nights into Estonian from Russian in 1984.
Seppel married the Estonian poet Andres Ehin in 1975. The couple had three daughters, one of whom is Kristiina Ehin.