hahahaha.. man the dash kits they make for the mazda 3 really sucks and she likes her factory radio. Her car already came with a jack for the ipod so she can play it through her radio already.. BUt she can not control it through the radio.
Then leave it alone. The only way to properly do it (IMHO) is with a aftermarket head unit. The harmon kardon kits are expensive but with stock units that they fully connect to they fully control the ipod and sound awesome. But for the cost of it you could buy a aftermarket HU that supports direct connection to the ipod.
Get her or build her a nice dock for the Ipod so it is easier to control while hooked up to the stock head unit. I bought a Griffin iSqueez to hold mine while hooked up to the deck but depending on cup holder placement in the car that may not be the greatest option. And then you can get a charger (if not already) and have it all hooked up nice instead of just laying on a seat.