Gary say's it's cos your dog's crossed with a freisan and you should get some work done instead of watching your dog eat grass,
Seriously though i would'nt sop her from eating grass there is'nt a proven theory why dog's do this but it certainly won't harm her, some say it's to clear there stomach's or lack of something in the diet or even boredom etc; don't think it's anything to with her comeing out of season mate, since i started useing Garlic, parsley and cod liver oil that come's as one oil from WCF my BullX dose'nt eat grass half as much.