Dalzell Shower Screen Consultants here, at your service Sir!
Does she want you to do the job, or just after information?
If it's real glass (strengthened/safety of course) and the marks are on the smooth side - i.e. opposite to the design, why not try a scraper and a WHITE scotchbrite pad, that should take of most guff from shower screens. It's normally dried in suds or microscopic skin flakes which have been left behind after the water slides down the screen and tiles. Grout + Tile Cleaner will probably do the job too, but if you're REALLY stuck, MDR is the stuff . . .
http://www.titanlabs.net/mdr.htm from the same folk that make GG3+4
I don't know where you'll find an inconspicuous spot to test these different methods in a shower cubicle, but best of luck.
My note of fee will arrive in the post shortly.