This girl, 16 /17 - this is high school age - is she enrolled in any school? has it got boarding option? If not, ask your solicitor to find one for her.
A good excuse - the last 2 years of high school is very important for getting into a good uni. Enrolling into a boarding school will ensure her English will improve much faster, and she can concentrate on her study.
The girl has powerful family background, enough to annoy 62 - this means there should not be any issue with money and 關係 - move her into a boarding school and get them to change guardianship ASAP. If she has no other family member in OZ, can arrange for a solicitor to take up this responsibility.
Any further problems in China - leave it with 62 & 99 to sort it out themselves.
Oh - in case she is here for English course or foundation course (since it is mid year already, so assume she is not here to enroll in a proper course at uni):
1. explain to them that English course are only interested in money, boarding school will be more effective in improving her English.
2. foundation course (a bit trickier) - tell them that the 2nd bedroom is already set up as a nursery. It is better for the girl to stay at colleges at uni - make friends, practice her English, etc.