I'm sorry she made you feel stupid. Not a way to make a sale. I have a flannel with soccer balls on it and it was definitely in the juvenile section. You just never know on some themes.
As you said though she's a wonderful teacher so only you can decide if decent 80% of the time is worth the other 20%.
Not sure how it is in other areas of the country but for some reason attitude shows itself more often in quilt stores than any other store I shop at. Not just from owners but sometimes the clientele as well.
I had went to a new LQS and they were having a class in the back. One of the customers thought she shouldn't have to wait for me to check out first as she was taking the class and shopped there all the time!
I was gracious enough to say if she was in a big hurry then please go ahead of me. After she went back to the class the lady checking us out whispered a thank you. The customer sure didn't.
Wish I could say this is my only example but I have plenty others. Along with those I have wonderful experiences as well though.