How should I deal with such matter?

Maybe you can have a chat with her to find out what are her concerns? Whether or not she is having some family issues back home or is there some other issues (feeling overwhelmed?)? It could be that she is unclear of what is expected of her or perhaps she is having some difficulty? Sit her down to have a chat. If you think that she is capable and would like to keep her, see if you could make some adjustment to address her concerns. It could be that she is having some family issues and would need to settle that as well. You could also speak to your agent and let them find out what is the issue.