Reply To: No mechitza?

Gray Matter. Why do you assume a coworker would outright turn down a polite invitation.
As for kol isha, i’m, really not concerned a non frum teenager with mental disabilities, as the OP puts it, would do much singing of zemiros. The point here is, the coworker in this scenario (I highly doubt it actually happened) is not being very nice and friendly as he takes a dig at frum people, no reason to respond in kind, but invite them to see how beautiful it is to keep shabbos, the torah way.