Is this the condition for them to return the money?

(Not sure how much you gave your auntie.) I intend to tell them forget everything and cut-off all relations. Not sure if in China, if you can official cutoff relationship.

If these are additional (on top of the money you gave to your auntie), I really do not know what to say. If your mom has other siblings, maybe get everybody together and discuss this.  Of course, if you have siblings or good friends in China know judge, you can go to court.