Thank you for using JustAnswer.
I am sorry to hear about your situation. If you're not trying to get any medical information (that is, letting them know that you know your significant other is a patient and just trying to get an appointment) then it's true that this is not a HIPAA violation. They're wrong about that fact. But note that this is also not actionable by you. They have no obligation to get the law correct. Now if they are incorrect in their interpretation of the law (thinking that something is not a HIPAA violation when it is) they can be liable. If they're incorrect in interpreting it so that something they think is a HIPAA violation when it is not, they have no liability. As such, MOST doctor's offices tend to be incredibly conservative in how they interpret the law, as there's no downside to interpreting it more broadly (except for unhappy patients).
The ADA does not apply here, as this is not an "accommodations" issue. They have no obligation to allow you to set an appointment on her behalf, I'm sorry to say.
I know this is probably not what you wanted to hear, but it is the law. I hope that clears things up anyway. If you have any other questions, please let me know. If not, and you have not yet, please rate my answer AND press the "submit" button, if applicable. Please note that I don't get any credit for my answer unless and until you rate it a 3, 4, 5 (good or better). Thank you, ***** ***** luck to you!