Lonyo: it's been way too late for the car makers. It is only in 2007 that cars are going to start getting iPod connectivity. Few cars these days have support.
I got an Alpine CDE-9845 which has a line-in, but it's in the back so you'll have to do some creative cable routing. (It's beyond me why they would put this input in the back) A head unit with a line-in is going to sound way better than cassette or FM transmitter. That was last year's model of course, but there is probably a newer model for this year with the same feature.
If she can afford a BMW X5, she can surely afford a nice Alpine head unit for her iPod.