Passport Of A Nigerian Confiscated By Employer In Oman

Hello All, please help in any way that you can. My cousin is in Oman doing housemaid (we just finding out) and her mother passed away three days ago suddenly. She is trying to come home for the funeral but her boss took her to the agent's office where they beat her and sent her back to her boss house. Now her boss has her passport and will not release it. She paid 500k to her agent in Nigeria to help her process her visa and they are paying her about 50k/month for working all day. Please help us. Anyone with similar experience? How have you gotten through it? What can we do in this instance? There is no Nigerian embassy in Oman.