If the girl has limited money and stays in an Indonesian village how would she have been able to repay the 4100 pounds in the place ?

Its more so that maybe the girl if this is kosher, is worried she might be asked aside at our border to be chatted with.
Germans can get the Aust WHV which is easy, but Indonesians find it harder under the Aust W&HV system.
Can't predict what (former) Aust ABF/now Dept of Home Affairs officers will do per individual case, whether the girl will have it easy when she enters Aust, is conjecture, she might have it easy, or she might be chatted with, and her items swabbed for substances.
Who knows.
If the girl has applied for the Aust WHV, under a German passport, she could have applied on line, so maybe she has applied under the Indonesian passport, where she would have needed to go to the Aust High Comm/DFAT's VFS services.
If this case is kosher, she might find it hard when she enters, and is asked aside.
The former ABF/now Dept of Home Affairs officers can be quite tough in their questions, and the questions can be the same but asked by 2/3 officers, and if anything is different, or if the person does not want to answer, it can go pear shaped fast.'t
I'd be very surprised if the girl had a German passport, that's not the way these relationships generally work.

Indonesian law at the moment does not allow dual nationality, according to the Jakarta Post.
So she would most likely have applied under the Aust W&HV for Indonesians (if kosher).

Sorry for the late reply.
I already did report this to the Border Force website. However it has failed to work and she is now in Australia.
I just have to move on but cheers for the advice though.

Pretty much seems that way in this scenario and I'll just have to be more careful next time.
Thanks westwood

If she's due to leave Australia this month, revoking her visa is not going to have much effect at this late stage, even if it could be arranged, which I doubt. You've been scammed, nothing you can do, accept it and move on.
I did report her to the Border Force website however she was still able to enter Australia a friend of mine said.
I'll just have to move on and be more careful in my next relationship. Thanks libbyth