Do it now.
But what if things didn’t pan out and she has been replaced/let go?
Canada News Wire may not have the announcement.
And you’ll look pretty stupid if your congratulator note gets handed to the new Chief Financial No-Nonsense Officer, won’t you?
Just call the main switchboard; tell them that you have a letter to mail to “Gail Smith, your Chief Financial Officer” and ask if you have the correct postal address.
If Gail is still there, what you read off will be confirmed.
If Gail is no longer there, you’ll be told.
This method is better than asking to be “Put through to Gail” because you don’t get into a gatekeeper dialogue “What’s it about?”, and you don’t suffer the embarrassment of having to hang up and leave your phone number staring her in the face.