Is what this homeowners insurance company did legal?

I live in California, thankfully not down south in all the fires, but up north in the Bay Area. Today my stepmoms book keeper showed her a paper from her insurance company stating that they were cancelling her homeowners insurance because she has too much stuff in her backyard and that they discovered this by flying a drone over her property! Is this legal? They had no reason to redetermine her eligibility, she hasn’t filed a claim recently, and I thought that legally people had a reasonable expectation of privacy that includes anywhere that is within a fence or otherwise stipulates this is private property? Can she fight this? It seems crazy to me that they can redetermine this based of randomly flying drones over homes they insure. Any advice is appreciated.