She's scratching the back of her ear, could she have an ear infection or ear mites? Usually they will scratch the inside of the ear, but maybe she has figured that out yet. poor puppy...
I absolutely would not be washing a puppy weekly in flea shampoo. You can get some Dawn dishwashing liquid, the original formula, it's a blue color. Put a thin light color towel down where you wash her, suds her up with the Dawn starting at the neck and working your way back. Let her sit for a few minutes and watch to see if any flea's jump off. If she has any, trust me, they will jump off within 3 - 4 minutes. Rinse the Dawn off good and then shampoo her with a good shampoo and cream rinse. Rinse her thoroughly. Be careful if you use a blow dryer to not let it get hot on her. Their skin has no protection from the heat and can get irritated from the dryer.
One other thing I would check is to be sure she has no mats. Matting can cause them to itch and scratch too.
If you've ruled out skin or ear infections, you may want to look to the food she is eating. There could be something in it that is making her itch.
Good luck!
