Is the money earned from a government job, in which my mother does not commit to the full required working hours to care for us, considering this a common affliction and a widespread practice among employees, unlawful for me to consume?

Your mother is not permitted to be absent from work, because an employee must adhere to the work schedule agreed upon in the contract. Violating it is considered betrayal and deception, due to Allah's saying: "O you who have believed, fulfill [all] contracts," and the Prophet's (PBUH) saying: "Muslims are bound by their conditions." If the mother is absent without permission, she must return the portion of the salary she does not deserve. What she has earned through her work is permissible for her. She must cease what she is doing unless she is granted permission for it.