This is a rather sophisticated scam indeed. Unfortunately you don't need such kind of sophistication level when it comes to non-tech users or as the OP puts it

This is a rather sophisticated scam indeed. Unfortunately you don't need such kind of sophistication level when it comes to non-tech users or as the OP puts it his "Mom".. because for them even a banner ads which say "you have one message waiting" or the ever popular "emoji in email" just works equally well.