I am so very sorry this is happening to you. If it's any consolation even if the insurance was in effect, I know that most insurances have a deductible and possibly some things aren't covered.
What did the tests say about her bloody diarrhea?
If she is still passing blood, she needs to see the vet immediately. That is very dangerous and especially in a puppy.
So sorry this happened to you right in the beginning. Karen519 makes a great point. Pet insurances usually have a 2 week waiting period before a claim can be made. Of course, if your breeder had actually activated the insurance she said she had, then Carly's illness might have been covered.
But if it's any consolation, most pet insurance is so very inferior to our 'people" health insurance that you may have actually gotten back far less than you would have thought.
Once Carly is well, you can try collecting a portion of what you had to already spend from the breeder. But if the conflict causes you more stress than it's worth, don't allow this to upset you during a time you want to be enjoying your puppy. If your breeder is an honest well-intentioned person, she will likely offer to help you with the costs if you tell her what has happened since you brought Carly home.
If at all possible, it's good to keep a good relationship with the breeder because over the years ahead, she can be a great resource for you.
Chance's breeder had sometimes identified some issues he has had even before my vet. My breeder REALLY knows her Goldens and I love her for it.