My 4 month old puppy keep biting everything how do I get her to stop? ?

I know she is teething and I have bought her toys. Ill even play with her so she has something to do. She'll play for a while then goes off and bites my couch, or hides under the couch to bite something else! I've moves all wires off the floor but somehow she still got to my iPhone charger (that now do not work)! My dining room table and chair are wood and now all messed up because she has been eating them. Another thing she is fixed on is toes?! She nips at, mainly, my boyfriend's and my toes in a playful way but it hurts and I say "No! No bite! Bad" in a firm voice, pull her away and give her one of her toys. She is very smart for a puppy she knows it wrong but does it anyway. I don't want her to be afraid of me I don't know what else to do, I need some help...