Do you know if she watches Yo Gabba Gabba at all? They've had some really cool bands on their "Super Music Friends Show", (like Jimmy Eat World, Hot Hot Heat, Mgmt...). Some of the songs from their "Super Music Friends Show" segment might not be too bad. I can look for a few too.
Unfortunately, my wife has gotten my daughter turned on to "Call Me Maybe" :\ So I know that one can be catchy to the 4-6 set as well.