Typically, realtors have someone cover for them when they are out of the office for religious reasons, vacations, etc. That's especially true on a high 'sale' day like a Saturday. I don't think this lady should get her fee. If she had really cared, she would have had someone covering for her.
I'm not Jewish...but there is that part about "Nor the stranger that is within your gates" in the Commandment. So there would seem to be some gray area there.