Making a Child Learn?

Take away the things most precious to her, Disney Princesses, things like that. You said the reward system doesn't work, but perhaps that is because she is spoiled (in your own words) and has many other things to occupy her. Take it all away. Anything that you do give her should be educational and fun. When you take her to the store, have her help you shop. Show her the prices and have her do simple math...I need 2 red toothbrushes and 1 blue one...how many toothbrushes do we need? (one for each member of the family). Learning needs to be as fun as the things that distract her, be creative. If she does get retained, don't make her feel like a failure, instead, look at it as an opportunity for her to learn everything that she needs to so that she can be successful the next year. It could be that the culture shock of moving to China, and back affected her and you should be patient. Get involved as much as possible with teaching her yourself so that she will know that you are willing to put in the work that you expect of her.