Both for her and for you! See what you can do together that gives you sort of a break from the pregnancy blues. Get some comedy DVDs and have a good laugh together. Hormones are probably running havoc with your girlfriend state of mind and it will get better but it's not easy. For her (and you!), it's really important that she eats well and healthy, lots of fruits and veg and so on, it will help her mood too. Go easy on the sugar. Try to get out for some fresh air and light exercise.
Does she have any pregnant friends to confide in, and if so, can't you meet up with their partners? It will help to make sense of this weird and wonderful time.
And the more resourceful and resilient you are now together, the better you will deal with all the exciting things the baby will throw at you!
Hang in there, it sounds like you are doing pretty good at understanding and supporting your girlfriend.