At what age, died a Saint Agnes of Rome?

According to St. Ambrose, Agnes of Rome, died by fire at age 12. Other versions of her martyrdom are given by Pope St. Damasus (r. 366–384) and Prudentius in Peris- tephanon. Agnes is said to have been a beautiful, wealthy Roman maiden. Agnes’s emblem in art is the lamb, a symbol of purity, and because of the similarity between her name and the Latin word for lamb, agnus. In art she is often depicted in flames and with a sword at her feet.