Oration 24 (on Cyprian), 9–11 — as quoted by Pitre (p 86)
Justina, in the face of danger, 'took refuge in God' and spent time 'imploring the Virgin Mary to bring her assistance, since she too was a virgin and in danger.'
No freely usable English translation of this passage is online, so the note keeps Pitre's quotation and links to the full text. Translation: as quoted by Pitre (Oration 24 is not in the NPNF selection).
Why Pitre cites it
The virgin Justina, in danger, 'imploring the Virgin Mary to bring her assistance' — a fourth-century record of asking Mary's help, from a Father who defended the divinity of Christ.