As I said earlier in this thread:
OP-
"She shares her office with a male colleague and has no problems shaking hands with men... "
She has shot herself in the foot right there. Big time.
Document every interaction/handshake she has, document the time spent in the office with the other (non-related) male, and then proceed to sack her.
She cannot selectively choose which parts of her religion suit her work life.
Either she is all in or she isnt. That she handshakes other non-related men is seen by "some Muslims" as a big no-no, but she does it.
So to claim she cant be in an office of other men is fucking utter horseshit.
Dont let the tail wag the dog. Give her one chance and if she refuses, sack her.
Its that simple. And before anyone claims I am being anti-Muslim/Islamic etc, I am of the same faith.
There is NO protected characteristic at stake here.
Under two years employment, I'd frankly sack her sorry ass immediately for blatant insubordination and refusing to carry out tasks commensurate with the terms of her employment.