What is the Sharia ruling on a female employee's non-compliance with full-time attendance at the Ministry's branch office during a work assignment, or when salaries are withheld to save money for employees, with the knowledge of the employer? And what is the ruling on a female employee leaving for her home before the end of official working hours when there is a general directive to go out and participate in marches, while she does not participate in them and the officials are aware of this?

There is no blame upon you for committing to work only during the meeting hours, as long as the employer has granted permission for that. What matters are the terms of the contract, and the contract is the law between the contracting parties as long as it does not violate Sharia (definition).

Work supervisors are not permitted to disrupt people's interests for the sake of political demonstrations, as the authority of work is tied to the common good. If you are able to remain in your work and do not fear harm, then that is what is obligatory. Otherwise, you may return to your home. You are not permitted to participate in mixed gatherings or sit-ins where you fear fitna (temptation/strife).