YES, YES, definitely Juli, they're great! Their current single is Dieses Lieben. You could also try Silbermond, they're about the same as Juli, they only have one band member more.
LaFee is a popular 15-year old girl who does pop/rock, check out her singles Virus, Princesschen and Was Ist Das.
Also, Christina Stürmer, she's Austrian, but makes music in German as that's her native language.
Check out Ich Lebe, Engel Fliegen Einsam and her current single Nie Genug.