Is the remuneration received by a female teacher during her long sick leave due to work-related psychological conditions – when her health improves upon being away from work and deteriorates merely at the thought of returning – considered permissible (halal)?

If the employment contract permits cessation of work while receiving pay, then the money is lawful, for "the contract is the law between the contracting parties." If the contract does not permit this, then it is not permissible to take the pay, even if a doctor grants leave.