Hey Bill, dogs are chewers by nature, its their main tool of exploration!
At 3 months old, she is just trying to put her jaws on basically anything she can, what you can do is tell her what she is allowed to chew by giving her toys, and what not - simply say "no" in a firm manor - that means aggressive enough for her to stop, but not too much. If she doesn't stop, you're not aggressive enough.
When she gets to about 6 months old, her teeth will start replacing for permanent teeth, and then again she will begin to chew but on different materials.
Toy suggestions for dogs her age are small rope-like dog toys
and after her teeth gets replaced you should get tougher toys.
More information can be found on my hub - What You MUST Do As You Bring Home A New Dog - Part I