Tbh, I've done it before too. But thought I'd go about it the legit way now they've introduced it, so I added me mate.
However, surprise surprise, it doesn't appear to work.
In My Account, go to Tickets, click on the game (in this case Cardiff home) and click Forward Ticket at top. A window opens, but the 'Forward Ticket' button is inactive/dead/greyed-out whatever you want to call it, so can't actually do owt.
Back to the original plan then, just give them the card. I did try - don't know why I bothered.