Hi
When you order 'regimental' certificates from the GRO, they must be treated as 'Overseas' events even though they occured in England. Once you have navigated to the overseas section, you have a freeform text box in the order screen after you enter the name to enter the regiment, place, volume and page details.
If you ordered it as an England event, the GRO's system will reject it as the volume and page numbers do not match with those being used in Manchester registration districts at that time.
Although the certificate should contain her mothers maiden name (it might not), it won't contain her parents ages.
Dawn