Boondoc,
There is acceptable and unacceptable behavior. I have had patients who pick the plastic covers off the furniture right in front of their parents and parents act oblivious.
No I think your receptionist was right on for stating this was unacceptable behavior.
Why was she seeing you as a new doc? Because she wasn't happy with her old doc. If she wigged out on a 20 minute wait, she did you a favor and self triaged her family out of your practice.
In our office we would put a yellow sticky note stating she walked out of an appointment because of a 20 minute wait. IF I am flexible to let her in there would be a $60 no show charge (regular 15 minute appt is only $15, but she left 4 slots.)
I probably would not let her back in unless I was feeling very mellow. Anyone with such unrealistic expectations would make your life miserable.