St Hilary thought that Our Lady might have minor imperfections. He followed the tradition of Eastern Fathers. Looking at this verse from psalms:
“My soul is consumed with desire for your judgments”(Ps 119:20)
“A sword will pierce the soul of blessed Mary, so that the thoughts of many hearts might be laid bare (cf. Lk 2:35). If this Virgin, made capable of conceiving God (capax illa Dei Virgo), will encounter the severity of his judgment, who will dare to desire this judgment?”Hilary of Poitiers ,Tractatus super Psalmum 118, 12; PL 9, 523.
Gambero, L., 1999. Mary and the Fathers of the Church 1st ed. Translated by Buffer, T., San Francisco: Ignatius Press.