How do I sync friend- shared google calendars? I have an iPhone, iMac, Macbook Air and a girlfriend. So far, so good.

I have multiple Google Calendars that sync perfectly to my iDevices. 

The trouble is, I haven't found out yet how to sync the calendars my girlfriend shares with me to the iPhone. They do show perfectly on the Macs though.

Could anyone share the procedure if they managed this arcane spell?
I have exactly the same set-up :)
Mac, iPhone, iPad and girlfriend. I've got a bunch of calenders, and so does my girlfriend.

In Google Calenders, hover on the agenda you want to share and hit the little arrow on the right. A new menu pops open and select "Share this agenda". Now you can invite other people to this agenda by submitting their e-mail address. And you can give them rights (read, write, read/write...)

I hope this works! If not, please let me know cause it's a delight to work with a Mac, iPhone, iPad and girlfriend. Trust me, I know ;-)

EDIT
To get the agenda of your girlfriend, look for the label "Other Agenda's" on the right and paste your girlfriends' e-mail there. And if your girlfriend has shared her agendas with you, they will appear on yours.