Does it really matter who did it?
A big part of what makes this situation so fucked is that any random horny CD guy could get any woman he wanted kidnapped to become their personal "concubine" so to speak. Ginny was probably shown in newspapers along with other revolutionaries like Dragon and caught the eye of someone up there.
It really doesn't matter if it's Garling, Garling's son or any other CD or family because Ginny never cared about them and they clearly never cared about her either.
The only father that could have some form of impact would be Saturn himself due to his relevance to the arc but given how the Gorosei act and how old they are it's kinda hard to think he would do something like this on a whim out of just pleasure.