Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Ālecto, ūs, f., = Ἀληκτώ, οῦς (found only in nom. and acc.), the name of one of the three furies, Verg. A. 7, 341: Alecto torvam faciem Exuit, id. ib. 7, 415: luctificam Alecto ciet, id. ib. 7, 324.