I'm sorry, but when you're employed by someone... and they're paying you... they have a certain amount of control over what you can and cannot do
and I'm not being racist... if a white christian wants to wear a crucifix around their neck to work and the employer says you can't wear jewelry to work... then don't fucking wear it! and if you do, expect to get sent home or eventually fired
and you gotta think of this... if they let this woman slide... then other employees will try to get away with things and say it's part of their religon... if the company says "no, you can't do that" the employee is gonna turn around and say "oh, well you let that one lady wear her hijab... you're discriminating against ME"
that's why they have to keep it uniform among all employees
companies have rights to enforce dress codes and other policies
or how bout this for an example... let's say I work at a retail establishment... and our busiest days are on the weekends, therefore all employees are required to work Saturday and Sunday... this rule is established when I start, I work on Sunday every weekend for 3 years... then all of a sudden I say I can't work Sundays anymore because of my religious beliefs... is the company supposed to say " ok, no problem... we'll change our policy for you"
fuck no
when you work for someone... they have the right to tell you what to do and what to wear... period... don't like it? quit!