Among the disciples of the apostles in the primitive age of saints this holy virgin shone as a bright star in the Church. She lived when Christians were more solicitous to live well than to write much: they knew how to die for Christ, but did not compile long books in which vanity has often a greater share than charity. Hence no particular account of her actions has been handed down to us. But how eminent her sanctity was we may judge from the lustre by which it was distinguished among apostles, prophets, and martyrs. She is said to have been a daughter of the apostle St. Peter; that St. Peter was married before his vocation to the apostleship we learn from the Gospel. St. Clement of Alexandria assures us that his wife attained to the glory of martyrdom, at which Peter himself encouraged her, bidding her to remember Our Lord. But it seems not certain whether St. Petronilla was more than the spiritual daughter of that apostle. She flourished at Rome, and was buried on the way to Ardea, where in ancient times a cemetery and a church bore her name.
"The inner life of another that is known to God alone becomes to a much less degree open to us through friendship. It partially fills the desire of our incomplete, lonely hearts for completeness in another. Friendship brings out the best in a person through forgetfulness of self." - St. Thomas Aquinas