What is the ruling on women gathering with men in one assembly?

If the men are mahrams to the woman, then there is no harm in her sitting with them, provided she is modestly dressed, covering what must be covered. However, if they are not mahrams, then it is not permissible for her to sit with them, based on the Almighty's saying: "And when you ask [his wives] for anything, ask them from behind a partition. That is purer for your hearts and their hearts," and based on the Prophet's (peace be upon him) saying: "Beware of entering upon women."