So I created a calender event through Siri for my mom and dads surprise anniversary party only to find out she emailed the event to my mom. My mom wasn't on the invitee list... Siri just emailed it automatically!! What if I scheduled "fire John Doe at 8am on Friday"? Yes, John gets the heads up!! Bad Siri!!
Thanks for the heads up. I haven't had this happen but I've just thought of a simple work around.
I have the same set up as you. My mom is listed in my contacts along with her email address and Siri knows she's my mom. So when I plan on having Siri set anything confidential or a surprise I'll simply tell Siri a different name (code that I know the person by).
Example: If my mom's name is Monica Smith and Siri knows this, I'll use my mom's maiden name (Monica Doe), a nick name that family and friends call her (big mama) or her initials (MNS). My Siri does not know any nick names, maiden names of my contacts and I have no one listed in my contacts by their initials.
"Siri add surprise birthday party for Monica Doe on March xx, 2012."
"Siri add surprise birthday party for big mama on March xx, 2012."