True that

Precisely. Our dark lord and savior is not pleased with this woman.

That just promotes the idea that atheists believe in and worship satan. Many atheists are trying to stop this belief because it's far from true and gives us an even worse name than just flat out not believing in satan would.

Sorry to say, but any competent person knows the deference between atheist and satanist. At least, most people. Some morons don't get it, but it's not the fault of the people who kid and joke about Satan being their God, ruler, etc.

Or OP could just stop her, tell her she had a line up and what she is doing is inappropriate and to move on. Once you start agreeing, or show any kind of interest, it's hard to get them to back down.

Why should she be forced to go to a group meeting for something she doesn't believe in? Would you tell a Muslim to go to a meeting on the wonders of bacon even though it violates their religion?

I don't think they actually meant to /go/ to the meeting. Just get the address and get the religious woman to move along. Though that will likely backfire when OP doesn't show up and the woman comes back to find out why.

The customer was most likely screeching about how the end of times is coming, that Obama is the Anti-Christ, or other stupid things Religious zealots scream to try to get people to convert.

DoyoubelieveintheLordandSaviorJesusChrist? No? Then let me tell you about him. <insert rant here>

When I look at the facts, a person has a limited amount of time at the cash register. I'm a Christian, and I would never attempt to share my faith in that setting, because that's not the place or time. Not enough time either. The fact that in Canada we are given freedom and freedom of speech, if the employee said to me "how are you today?" I might reply by saying, "I'm having a great day. Just got back from a full week of camping at a Christian conference camp grounds" and I would leave it at that. I think there's a huge difference between small talk and bible thumping. I am against bible thumping. I believe the customer had a right to say how she felt. I'm still left wondering though, what could she have said in those few moments to impact OP so much?

It might have slipped that OP wasn't religious or was atheist and the customer took it upon herself to force a religious rant on them. Really, finding out someone isn't the same religion as them is enough to set people of on rants.