Okay I have a book called the Food Doctor and I looked under PMS and these are the foods it recomends to keep everything balanced and the symptoms at bay (hopefuly for your sake....and hers....LOL)
Here is the list: wholegrains, green leafy vegetables, dairy products, fish and seafood, millet, rye, buckwheat and brown rice.
The book also says that if a woman knows her menstral cycle is just around the corner, she should avoid tea, coffee, alcohol and chocolate.
I hope this will help and she will co-operate and try this for a couple of months.