Is a daughter considered sinful if she refuses to return to live with her mother in her home country, where there is no source of livelihood for either of them, and the daughter is working to support her mother, given that her return would make her a burden and cause problems?

If your work is permissible, then you are not sinful; rather, you are rewarded. We advise you to try and convince your mother and appease her, and to commit to contacting her. If you can stay near your mother with sufficient money for both you and her, and she has no one to care for her but you, and your absence is only for the sake of increasing wealth, then we advise you to return to her.