it's fine to do, and the more often you give a bone, the better the cleaning effect on her teeth.
For recreational chewing you can give beef knuckle bones (femur), neck bones and ribs for example, but do
not give the middle part of the femur - it is the most dense part of the largest, weight bearing bone in a cow's body and can break your dog's teeth. This part of the bone is commonly sold as "marrow bones" in little O-shaped slices packaged on styrofoam trays at supermarkets.
You can see an image of a bone here:
http://forums.ourdogsonline.com/showthreaded.php?Cat=0&Number=229&an=&page=0&vc=1
The whole bones, like in the photo, are fine to give, just take them away when the softer joint knuckles are chewed off.
Sheep, veal and lamb femurs are nice too.
Check out the meat departments of grocery stores and (if you have any) local butchers.