There needs to be wider education about the dangers of lazer play - it more often than not result in OCD light and shadow chasing. GSDs seem more prone to the OCD behaviour than some other breeds. Your dog doesn't seem to be too far gone, and if you stop now, and redirect her attention everytime she fixates on moving lights or shadows, she may forget all about shadow chasing.
Do a google search or a search on this board for light / shadow chasing, lazers, etc - lots of info there.
I'd start by greatly upping her exercise and letting her chase thing she actually can catch - let her catch the ball, rag, tug and let her posssess it - the catching and possessing are important instinctive sequences in a dog's prey drive.
How old is she? Her age will need to be taken into consideration as to how intensively you can exercise her.