How can a female student convince her mother to accept her working at a women-only company to fund her studies, knowing that her mother refuses her work on the pretext of finishing her studies first, and has previously refused other permissible matters such as wearing the hijab?

Resorting to Allah through supplication, and being patient with your mother while increasing your supplications. Involve righteous people whose words you hope she will accept. Discuss with your mother gently the issue of saving money and searching for ways to achieve that, such as work that does not require leaving the house. If this is not feasible and you need to work, and you might be harmed if you do not take the job, then there is no blame upon you for taking the job, while striving to please your mother, for obedience to parents is not obligatory in matters that harm the child. We advise trying to reach an understanding with your siblings gently and seeking help from good people to avoid discord.