Your daughter is very lucky and welcome to this corner of the forums!
There are many threads on this topic. The option I went with was installing the GROM USB-2 unit w/ BT adapter (may require a different setup/option for your specific car). The GROM retains stereo and steering wheel controls. It was a hassle to install but well worth it in my opinion.
If you simply want Aux, you don't necessarily need the ashtray setup. Check out P/N 84109237655 (AUX Socket) and 51459128397 (cover). But before you go buying these, triple check if you already have one installed. You'd be surprised how well hidden it is.
