"proffesional enough not to be using song sheets"
I've seee plenty of 'pros' use sheets, so blow it out your face...

"she sang the SAME songs in the SAME order, interspersed with the SAME patter I'd heard on the previous two occasions"
In what time span? Go on the road with any of the big names... If they're promoing a new CD, you'll get very nearly the exact same show with the same patter out of them for a year... and there's nothing wrong with that...

Or YOU try getting up in front of an audience several times a month with all new songs and all new 'patter'... And while yer at it, paint my house, and cure cancer, and rebuild New Orleans...

And whistle "Dixie"...