To send an employee to a client even though she refuses because of her religion?

You are not correct

This is tricky. Because how devout is devout? Does she pray during work hours? Does she receive any company benefits that she hasn't earned per se like company stocks/ dividends? (I ask that because a strict interpretation of Islam is that Muslims should not earn interest etc on money), does she wear full Burka only showing her eyes? Sometimes culture and religion get mixed up and people pick their values based on culture and cite religion as their reason. There are some devout Muslims who would have no issue doing what you have asked her to do but may have issues with things she is comfortable doing. To cover yourself, you could meet with her and ask her to take you through her beliefs and the impact this would have on the work place and her doing her duties. Then you could look into REASONABLE adjustments and I say that in capital letters because sometimes people think adjustments have to mean employers bend over backwards. No they only have to be reasonable. Get things clear now. She has a right to set her boundaries but you also have a right to set yours too. Hopefully a meeting and a plan in place will help get the best from her whilst also allowing her to follow her faith.

Taking your auntie to a professional meeting as a chaperone is the maddest thing I've read on MN for a while.
Do the people coming up with these "chaperone" suggestions work in the public sector perhaps? I can't think of anywhere else with an endless supply of available female staff and an extremely generous budget?

Can you just fail her probation? I would cover this instance by going myself and then fail her probation (and seek HR/ legal advice on wording) She refuses to perform the key tasks of the role despite having known what the role involves, so to me it’s reasonable.

Sorry yes, I don't mean everyone said that or that the OP did, but it seemed to be the first thought for several posters.

Lots of other people piled on with that. The OP asked:

AIBU to insist that she does her job and goes there or would that be religious discrimination?

How does it being Ramadan at the moment affect anything?

Maybe nothing can be done in the case OP has mentioned. It's a bit grim though that the first thought was how to get rid of this woman rather than see if there is any possible way of making it work. Even if meant the woman herself bringing in an aunt or sister to stand outside the door!

When we visit people in their homes or empty buildings obviously there are extra precautions. It’s not usually the same risk assessment for a known client at their place of work.

It’s Ramadan at the moment. Maybe that has some bearing on her decision? Maybe after Ramadan she’ll be ok seeing as she’s ok to share an office with a man etc

I agree. The thing is that examples you’ve given don’t cost money. How much would you be prepared to reduce your own income to support someone else’s religion? I think that’s OP’s situation because there’s not any other way to accommodate it

You do know it's Ramadan don't you? I mean surely a quick research into the Muslim faith would help you understand that being completely alone with men for Muslim women is a big no no. There are always creative ways of doing things and I don't see how it's such a big deal to be accommodating of people who practice a different faith to yourself. Why not ask the client if they have a female member of staff who can assist?

Did you tell her that she would be going to visit clients alone before you hired her?

I would put this back on her. Ask her for suggested solutions because she's refusing to do the job you asked her to, so lay out your very good reasons (will lose client if we bill them more, adding a chaperone will increase costs, no one else available to do this, we hired you thinking you could do the job, etc.) and also tell her how much you want to help her succeed and ask her what would she do in your situation!

I was in my first proper job (sandwich placement) when Suzy Lamlugh disappeared. She'd be 64 now. Maybe with grandkids.

Just because they believe it, doesn't make it true. Some people believe the Earth is flat.

Accomodations are a bridge.

Has she offered any solutions?

It is not only Muslims that need chaperoning. Years ago when HMRC did routine inspections they came to see me. The tax inspector was a man and he was obliged to bring a woman with him because I was a lone female.
My elderly aunt was having a downstairs bathroom built. Although the work was private it was being done by a company that worked with the local authority and the health visitor had recommended them. The architect came with a woman as he didn’t know I would be there and he said this was company policy.

That is a good point, and wonder what the protocol would be in that case.

I think it all can get quite confusing and frustrating.

Perhaps job descriptions need to be more detailed and covered before people are hired. "Would you have trouble working one on one with (insert possibility here) at their home, if needed?"

Probably identifying as a man for a day then.

I've had a colleague who was devout Muslim, (young, unmarried) and similarly unable to be alone, unchaperoned with men.

It wasn't a massive issue because there was always at least one woman nearby. If she was in an office with a man, the door would be open. If we had to send her to an area with only men, we would have just sent someone else along for propriety.

And I would absolutely not. Women should be able to fully participate in work without needing babysat for fairytale reasons. I would do absolutely nothing to support this.

I think I must have been lucky to have worked in sectors where people will try to accommodate the wishes and needs of colleagues and contacts. They may not always manage it, but the starting point would be 'what can we do to make this possible?' rather than 'how can we get rid of this person'. A Muslim colleague was given a cupboard to use as a prayer room so he could pray at the required times. Someone with a complicated visual impairment was allowed not to go to IT-based courses but to learn the content in other ways. People helped each other.

OP, say you refuse to provide accomodation to her religious beliefs in this and try to let her go.

What will you do if she comes back and says you asked her to do something she told you violated her religious principles and that her work until that point had been fine?

Will HR back you?

Does this look targeted?

Think about that before you refuse accomodations.