
Agree with others that there are too many treats. Three fifteen minute walks a day on a lead is not too much exercise. She needs to socialize and experience the world around her. What you want to avoid is exercise that puts to much strain on her joints - like jumping, or going up and down stairs, or running with her, or extended periods of exercise. Puppies and young dogs naturally run/jump/play in short bursts - then they plop down for a rest, or to dig a hole in your garden, or gnaw your wooden chair legs. :-)
If I recall from reading the kong filler ingredients at PAH, it's full of fat and junk. Try softening a part of her regular food with water and use it to stuff the kong instead. Or buy a few packs of Naturediet and use it to stuff the kong, but remember to feed her a bit less at her regular meal. You can do the same with any leftover plain meat and veg. Low fat cheese once in a while is fine.
Schmackos are junk food for dogs. Dentastix are in the same category. IMO opinion they should not be given to puppies at all and only once in a while to adult dogs. Try James Wellbeloved Crackerjack treats instead. I often just give my dogs regular pieces of JWB food as a treat - they are very partial to duck & rice - and are as happy with it as they are with food sold as treats.
Have you tried clicker training? Really short version is that your dog learns to associate the "click" as praise by using a food reward when you first begin to use the clicker and/or teach a new trick.