I don’t know about your mother, but my mother is not even a power user – Windows, hunt-and-peck typing – and she taught herself to use IRC because that’s what the other people in her social group were using.

I assume she didn’t use any /command except /join – maybe not even that, because if you’re only using one channel then you can have your client autojoin – but that was enough to get her in. Presumably she learned group etiquette on the fly, the way most people do.