What is my role towards my friend who works a night shift in a mixed-gender environment, and wants to work a morning shift to be able to obtain a visa for her husband who treats her badly, knowing that she married him under pressure from her mother and wishes to separate from him?

It is permissible for a woman to go out to work under certain conditions, but your friend's work in a mixed-gender environment and at night in a non-Muslim country involves forbidden things, and she must repent from this work. She is not obligated to strive to bring her husband if it entails forbidden work or lying, for lying is forbidden, and truthfulness with disbelievers is a practical call to Islam. Her marriage without her father's consent was a mistake, but the marriage itself is valid. We advise her to be patient with her problems with her husband and to supplicate frequently, and to know that hearts are in the hand of Allah, and that distance may breed estrangement. She should be keen to reunite her family and start a happy life with her husband.