Question about international jurisdiction

[MargaretC]

My friend, an American citizen, is living in China and is having difficulties in her marriage, with her husband (also a US citizen) being verbally and emotionally abusive, lying and threatening physical violence. She is concerned about the legality of taking her children and returning to the US. What are her rights? What help can she get? Can he come and take the children from her when she is certain they are potentially in danger? Where can she turn for help?
This situation has escalated recently and she needs some advice as quickly as possible.
Her home state is New Jersey.
She could use information about legal rights, women's shelters which might help - anything at this point. She wants to ensure that her children are safe.
Thank you.