Given that you're describing your Mum in the same fashion we typically all do (And to avoid the "Yes, she's actually very technical" bait-n-switch), we'll assum

Given that you're describing your Mum in the same fashion we typically all do (And to avoid the "Yes, she's actually very technical" bait-n-switch), we'll assume no. You're mixing the ubiquity and common parlance/popularity to suit your situation, but it doesn't work that way. FTP, IRC, HTTP, and SMTP are all ubiquitious, but not necessarily the most popular method for describing things, keeping in mind that we haven't fully shut the book on the internet == www. XMPP is the protocol that you're talking about here but you shifted gears midway through to say that she should know what instant messaging is. (which again, I'm gunna guess she does). Similarly, Email fetching itself has gone through one major protocol shift under her nose without changing the very nature of it, so to make claims that in the particular instance of messaging she should know the protocol is arbitrarily moving the rule-bar. (Bet you still have to try and explain the difference between http and https to her too, and that always ends with *sigh... just look for the little green lock. :P)