Why is my dog not eating her dry dog food??

It sounds as if you have food available at all times for your dog, which in most dogs creates a boredom with their food. Dog's are built to want to hunt/scavenge for their food, and they actually prefer this over having access 24/7. I would recommend giving the recommended meal amount, set it down for 15 minutes and anything uneaten gets picked up and given again at the next meal time. Some dogs will choose not to eat for a couple days, and this is fine as long as they're drinking and acting normally. You could also try presenting the meals in a puzzle toy, or snuffle mat as some dogs just really enjoy working for their food instead of eating it out of a bowl. My other trick is to add hot water to the food and let it sit until it cools down.

Based on my understanding (her activity level is the same, interest in other food, hopefully drinking too and having normal output, I wouldn’t think this needs medical intervention. I think she’s telling you that she no longer likes that food. It can happen, sometimes after months or years of a dog happily munching on dry kibble or wet food. You might have to try a lot of different products until you find the right one. If you purchase through Petsmart Petco or Chewy, last I knew they have good customer service programs where if your dog snubs what you bought, you return/ bring the receipt with an open bag/package of food they’ll issue a credit towards the next while you’re trying to find the right match.