New Dog Owner Here. Cross Breed: Great Pyrenees- Mountain Cur

I would try to add a source of calcium like bonemeal powder to what you're giving her. The better pet stores also sell frozen raw food that consists of meat with ground bones, vegetables etc. If that fits your budget you can try that in place of plain ground chicken. Be careful with ground beef or lamb mixes at the pet store though as these can be very fatty.
The fish oil can either be mixed into the food or given separately. As long as your pup is doing well and looking healthy what you're feeding her should be fine. Most, though not all vets are surprisingly ill-informed about nutrition and will continue to push commercial dog foods and prescription diets that have weird ingredients like corn gluten. My mom's family dog in India was fed a largely vegetarian diet except for eggs and lived to a ripe old age!
Our dog was already spayed when we adopted her so I'll defer to others for advice about that.