I'm with HaydenAsche and The Dom. They're not too difficult, and plus if she really likes the Postal service, she can get into Jimmy Tamballero's solo project, Dntel, which I find is amazing.
If she likes the Rnb / Dance type stuff, I guess going with some Debbie Deb or Madonna might be good as well, but then you might not like it.
You can also blow her away with some
Gang Gang Dance but it really depends if it's going to cost you the CD player or not, although I'd say it's worth it