Is it permissible to sit in a gathering that includes women who are not mahram (relatives one may not marry)?

Question:
He says: Honorable Shaykh, may Allah grant you success, is it permissible to sit in a gathering that includes non-mahram, such as the wife's sister?

Answer:
There is nothing wrong with it if they are a group and the women are covered and not mixed with the men, for the women are on one side and the men on the other; there is no harm in that. Yes.