HIPAA doesn't say any of that, although some of what you stated involves the ADA (Americans with Disabilities Act). There's no need to refer to case law - just read what is stated in the Act (it's the Health Insurance Portability and Accountability Act). HIPAA doesn't prevent restaurants or hotels from asking about service dogs or medical information, although the ADA does to some extent. HIPAA sets national standards to protect medical records and personal health information, but it apples only to health plans, health care clearinghouses and health care providers that conduct certain health care transactions electronically. Your sister, as a doctor, would be a healthcare provider and therefore subject to the act. Restaurants, hotels and Disney are not.
To the extent that HIPAA would have any application in the area of vaccine passports, it does give patients rights over their own heath information, including rights to examine and obtain a copy of their health records. If someone wanted to provide the federal government with a copy of their own health records, including a record of being vaccinated for COVID through the state, no state could refuse to provide it.