My Illogical Theory
The 'ghost girl' concept was introduced in Gen IV in DPPt, but not in HGSS.
It appeared again in Gen V it appeared again in BW.
Again in Gen VI in X and Y, but not in ORAS.
There were no ghost girls in ORAS and HGSS. Why? They're remakes.
As there were no ghost girls in Gen II or Gen III, there is likely to be none in their remakes. That isn't really the 'ghost girl' of the game since it didn't have any dialogue, but it's probably just some sort of easter egg (that I found btw WOOO). If you want, you can make it your ghost girl for the game though. It's not like the ghost girl is an official thing or anything.
But apart from that, no one has said anything yet on a ghost girl appearing, likely due to the games' remake status.
EDIT: As the commenter below stated, in Mt. Pyre that is a woman who reiterates 'No... you're not the one...' but this isn't really the ghost girl since she didn't have a full on cut scene, she was just a normal NPC, just referring to X and Y.
Hope I helped. :)