I've not read the other posts, but excuse me if I'm going over old ground.
I'd suggest making BMW pay for it, if you can. The car was under their care; so whether it was hit into by a customer or not is quite irrelevant - they should fix it for you!
My insurance went up quite markedly when someone hit into my (parked) car, so try to avoid involving insurance companies at this point, because even the mention of it can leave a mark on your record. Obviously you're aware that even if you try not to tell your insurance company, if it is claimed via the woman's insurance, it will be recorded anyway, and you'll still have that mark.
Because of the age of the car, I would personally only be taking it to a BMW body shop; purely due to the fact you have a 7 year anti-corrosion warranty, which technically would be void in the area that is resprayed if you were to have any rust problems later in life. With a BMW authorised repair, this wouldn't be a problem. It's not easy to find a decent BMW body shop however; though from the reports I read (and incidentally, who I went with) I would recommend Cotswold BMW. Not a 100% perfect job, but as near to it as you're going to get I'd say, and the colour match was absolutely perfect (which was my primary concern).
I know how you must feel about the car; that it's now not perfect - especially as I know yours is a low mileage car which you only use for fun. What I can say is that I went through all of the same emotions that you probably are right now, and even though I didn't think it at the time, it does get easier. The process of getting it fixed is NOT nice, but once it's all finished and back to you, you'll never think of it as having had a repair done - or at least I didn't, and I am very fussy about, well, everything.
There may not be any positive side, but try to think of one, somehow. For me, my sideskirt was chipped in the usual place (at the back, where it 'flicks' out), and of course the car came back without any marks. Whilst it was in the shop, it also allowed me to rectify the front bumper where the previous owner had slightly dinged it, and it meant it was cheaper.
I hope some of that helps, and it isn't too much of what others have already said.