It looks to me like the screen shot of the notification your mother received is not an email generated by Zoom. Please check the "From" address to determine the source of the email. You or an email-savvy friend can also look at the email "headers" which contain technical information about the source and traversal of the email, which might help in determining the actual source of the message.
This situation is not uncommon... where someone deletes a Zoom Meeting from their Zoom account, but a calendar entry is still in place in someone's email/calendar software, which does it's best to remind the participant of the meeting. Someone has to locate that reminder and remove it from the calendar.
