Seems your sister does not have connection

to higher power people; at the same time, she is not “潑” either. In other words, she is a normal "老百姓". What do you expect she will get if she tries to fight? Best for her is to send the money and get her passport back (and make sure she will get her passport back before she hand the money).

After she left the country, you can use the evidence (the photos and etc.) you collect to do whatever you want.