Christmas Cards? Did Clark W Griswold buy a SCUBA tank?
I am very worried that are asking us "how to convince her and what tricks can you use" and I strongly recommend that you read the incidents and tragedies threads and remember how dangerous this sport is FOR PEOPLE WHO ARE ALREADY PASSIONATE OVER DIVING.
Now, consider just how much more dangerous it could be if someone is afraid of diving but dives anyway because she/he was TRICKED or COERCED into diving.
Then ask yourself how valuable your own life is to you. Seriously. Because while she is diving with you and one blink from panicking - you have to be more than just her buddy - you are her life support and you should accept the fact that you are diving SOLO. If something goes wrong, it is all on YOU to solve it, whether it be your gear, her gear, or any other diving anomoly that creates a chain reaction of errors and complications.
You become safe, skilled, competent by enjoying diving. You must respect diving and love diving. this isn't gardening. Or tennis. Or golf. It is a hobby with an extreme amount of risk. Maybe she is more aware of that risk than you realize and has decided her life is not worth it.
She has four children. Maybe she doesn't want to do anything that could cause them to lose their mother.
You should respect her decisions and not ask strangers how to coerce and manipulate her. If she SUPPORTS your diving you have 50% more than divers who are married to non-divers who do not support their diving. Those couples are out there. The non-diving spouse cannot understand why the time and money and energy goes into diving and resents that they are not doing things together.
Could be a whole lot worse. A whole lot worse.