Export Wi-Fi passwords from keychain I want to export all my Wi-Fi passwords and import it to the keychain of my girlfriends Mac.

Is this even possible? And how its done? With iCloud Keychain Sync this passwords should also be available on her iPhone, shouldn't it?
From the  Finder of original keychain file, press Command+Shift+G to bring up Go To Folder and enter the path:

~/Library/Keychains/
Copy the ser “login.keychain” file to the new Mac, do this with AirDrop, Ethernet, USB or any external devices.
On the new Mac, press Command+Spacebar to open Spotlight and type “Keychain Access” then hit return, this launches the Keychain manager app
Pull down the “File” menu and select “Add Keychain” and browse to the keychain file you copied to the new Mac, selecting Add to import the stored keychain data to the new Mac


Hope this helps :)