There's probably insufficient details in your scenario. The way it is written now it reads simply
that she was fired for not complying with an expressed requirement of her job and in that sense it
is not discrimination.
Firing someone for an inability to fulfill job requirements is not discrimination it is simple
practicality. Do you hire a paraplegic as a gymnast? Do you hire a pacifist as a bodyguard?
Visibility and being recognizable are an intrinsic part of a security guards function. Unwillingness
to wear the uniform would seriously compromise that function.
Certain requirements for every occupation. I do not see your correlation to "religious
discrimination" in the debate description, your point was not well-made. You might try re-phrasing
the question ??