This is down to the mediator, so you should ask them how they prefer to conduct their mediation sessions, before deciding whether or not to hire them. Some will prefer the session to take place with both spouses in the same room and with lawyers present, as this helps eliminate any misunderstandings. Other mediators like to keep the sides separate, especially if one or both of them have a history of substance misuse or domestic violence. Some mediators conduct online sessions too.