Leaving Oman without employers knowledge

Hii everyone.... I am posting this query on my friends behalf. She is a gynecologist working i Oman. But for past 6 months she has been working alone in department and is on call 24/7. she was assured that two more gynecologists will join by April but no one joined. She has already resigned but hospital management is not relieving her from duties. They wont give NOC. They are not even crediting previous salaries. She is planning to just leave Oman without employers knowledge. will this decision of hers will have any repercussions in future? And what about the Visa stamped in her passport?  Leaving Oman without Employers knowledge will affect her entry in GCC or any other country?
Please advise......