I would say, get a copy of the best and worst non-organic offenders, and keep it in her purse when shopping. If organic of the worst offenders is too expensive, then find another produce item instead.
Also, lots of cheap veggies like cabbage (coleslaw, cabbage salad, cabbage stir fry, sourkraut), onions, carrots, celery, the basics, are usually very cheap.
If she has the money (sounds like she doesn't), she might be able to contact a local farm and get a big box of "seconds" or soup veggies or a bumper crop, but you might have to buy somewhat in bulk. (chickens come in seconds too, they are chickens that got mangled a bit after death in the processing but usually are pretty good (sometimes missing wings or otherwise slightly mangled) I don't think you can get induviduals of those though...)
With meat, and dairy and eggs, the best you can do. (Though if she can't find regular temp pastuerized milk, I'd personally ditch it. homogenized, I'd handle for a while, if I knew I could go back to the other later. hormone free is another must.) Find out which local brands of butter are best, and do what you can there. Get coupons (there are often dairy coupons here). if worst comes to worst, the worst butter is still good for you if it doesn't have dyes. Eggs, I would get flax seed fed or organic ones, if I didn't know anyone who raised chickens for eggs. Are there folks with backyard chickens, or a small farm with chickens?
whole milk yogurt with live cultures (you can also let yogurt with live cultures sit out an extra 12 hours to make it more strongly probiotic, apparently most places are only allowed to let it culture 8 hours.) and no sweetners, whatevers cheapest and on sale (or make it yourself).
Meat wise, its a toughie. I'd definitely say hormone and anti-biotic free, and then whatever she can do, the best she can.
Honestly, I'd say 100 dollars a week, with good menu planning, isn't that tight, and can totally be done. We have 100 dollars a week for two of us (I know its different) but I'd say we eat very well off it, including all pastured red meat, and pastured eggs. Now, we don't eat a LOT of meat or eggs, and are lucky to have a great produce place, but we live in an extremely high COL area. I'm sure that with some menu planning and foresight, she will be able to feed her family fairly TF. And if worst comes to worst, remember that half of TF is in the preparation.
If you search the archives there have been a couple of recent threads about eating TF on a food stamp budget--might have helpful ideas.
