Polo is a good idea. Id roof rack our luggage. Its one trip with the folks 300km each league, then never to be repeated so why have a big car when are city bound and rarely use the thing.
Dont get me wrong I had an outback 3.0l and I loved it. Ive had a lot of Bimmers. So has her Dad the lucky guy, although at his age every man deserves a nice car, and lady.
If I was going to go a bimmer Id go the 330i or 335i simply for the power. But doubt Id fit either of those in her budget :-)
The 328i is pretty quick, but again I think she would be struggling with her cash.