"Sugar Baby Love" from the opening of the anime A Little Snow Fairy Sugar. Always puts a smile on my face. ^_^

The first half of ( ), by Sigur Ros, is pretty uplifting and just plain beautiful. Try it out if you're at all interested in Post-Rock.

Jonathan Coulton - I Feel Fantastic

Sounds pretty god damn happy to me. In fact, a lot of his stuff is pretty light-hearted. Especially Ikea and Mr. Fancy Pants. They might not have meaning, but who cares. They're awesome.

Well damn, I know you said you wanted the lyrics to have meaning, but most people find it nigh impossible to not be happy when listening to this song:

Patrick and Eugene - The Birds and the Bees

Also, The Divine Comedy have some of the best lyrics I've run across for pure wit and lilt, but they usually revolve around love&etc. The Certainty of Chance is a song that does not and I find it uplifting...maybe others wouldn't...

EDIT:: Completely forgot that Muse - Starlight is ridiculously uplifting for me. Really.

Maroon 5's "Sunday Morning" comes to mind. It's a fairly happy piece. If the girl is into instrumentals, you could also pass her Joe Satriani's "Love Thing", and "Always With Me, Always With You".

There's a musician over here who produces lovely acoustic music, he's not that well-known internationally (he's a jazz guitarist, but of the singing kind) but his music fits what you describe. I can't as of yet post the URL to songs, but if you want, I can PM them to you. How about it?

happy happy joy joy comes to mind
supercar's starlight can be pretty uplifting

Eine Kleine Nachtmusik by Mozart :D

'Such Great Heights' by The Postal Service. Winner.

Well, since I've been jamming on Guitar Hero II, "Freebird" immediately comes to mind...

thank you! so far only a handful of your recommendations turnup on limewire. I guess the rest are just too rare to be found there... :(

Well, I linked to all but the most common one in my post...