Your daughter seems to be undergoing insecurity and separation anxiety as she was very attached to her grandparents. Added to it is the required adjustment to a different place, culture, people and surroundings.
Instead of shock and anger, try to react with firmness and patience. It is important that you spend more time with her and be patient. Encourage the development of attachment and a sense of security. Explain limits of desirable behaviour very firmly. She has to learn that aggression is not allowed. Usually re-adjustment takes place, but some children take longer than others. If the problem persists, consult a child psychologist for assessment and intervention.