Damn, I must now hop in my DeLorean and go back in time til right before I said it was an Audi and fool her to thinking it the Bimmer she thinks it is

 

Go find another s4 at another dealership, send her a picture of it to see if she likes it, say its a bimmer, and its a awesome deal. Then buy it when she says ok, and never tell her it isnt a bmw. she will never know.

that or take out the bimmer, throw it sideways a bunch and tell her it has no control, need AWD

 

That idea sounds like more fun