This is unfortunate for the provider but indicates to me that she is likely inexperienced. Any well seasoned provider knows that this is a risk and nothing is certain until a signed contract and deposit is paid. She should have known better and as a result while frustrated, and shouldn't have threatened you or got angry. Like I said, unfortunate situation but out of your hands. These things happen and IMO she should have acted more professional in response. You did nothing wrong and fortunately for you you didn't lose any money and this provider still has two months to fill the spot.