You are one smart lady Cando!
The marriage cert for Hester is on line (on a tree for Hester Barbara MCCARTNEY) and guess whose is next to it?? However, not on the same day - Hester and John GRAHAM on 4 Nov 1864 and Mary and John DOWDY on 26 December, 1864.
Both marriages at The Manse Beechworth, according to the forms of the Presbyterian church, married by John K (H?) McMillan. John Dowdy says he is a member? of the Church of England. Mary Ann, as mehtfield has already said, signs her name clearly with the surname DOWDY, however her writing does not appear very steady and she uses a lower case 'd' for the first letter of her surname - 'dowdy'.
Unfortunately I cannot decipher the witnesses' names for either marriage - except for a Robert BURNS for Hester and John - but they do not appear to be each other (if you get what I mean!)
Hester needed consent of the Guardian XXXX(cannot decipher) as she was under age.
Just a point of interest - Hester's mother's married name was Mary Ann MCCARTNEY.
Sue, Hester's sister, Martha MCCARTNEY, was in Peckham, London with her mother in 1871 so I think Ancestry may not have the correct shipping information.
Cheers, Judith