I don't think the files would be encrypted unless someone encrypted them intentionally. They would be on the drive (likely) as regular jpegs. Can she get into safe mode, or is she completely locked out? I've had good luck removing ransomware with Malwarebytes, but it sometimes has to be run from a USB stick or CD and it's usually not easy guiding people through the process of running things from a command prompt. I think your idea of booting from another disc and recovering files would work too. Depending on how many pictures you want to recover, it could take some beefy external storage. If you could just get rid of the ransomware, I might try that first.