Hi
From the passenger list on the Qld state Archives site, Emma appears to be the only Gardiner, or any similar name, on the Conroy so I would guess she was alone and most likely not a young child.
Are you searching for an Emma who left England and you dont know what happened to her, or are you searching for an Emma who married here?
mum mum
The Emma Gardiner mentioned in the link posted can't be the one born 1854 if she married in 1865, I know they did marry young, but 12 without parental consent is a bit young I think?
Is this the Emma you are after?