My niece sucks her thumb at age 9 almost 10. Could you give me advice to help her stop?

She is going through a lot. Her mother works all the time, father doesn't work (don't even ask, she won't leave). House is always a mess., no money for things,etc. Plus she loss a brother when she was young, she is a middle child, no one pays attention to her except to harp on her thumb sucking. Her life s a mess. Any suggestions would help and I will try and help her the best I can.