Hmmmm...Well, this could take a bit of "standing firm". YOU are the one who decides how you spend your dollars and your time.
If the class is free, then a good business person would make the kit available, but charge full price for it.
If the class is not free, then a good business person would make the kit available for purchase at a discount on the day of class.
Details, including special tools or notions should be noted on the package. That is in addition to reviewing in class everything necessary to comple the project. It's called "full disclosure".
In my humble opinion :roll: , this shop owner is running the risk of alienating customers with her "hidden charges". You could always take the kit back to the store, let her know you discovered her "hidden charges" and give her the option to either take the whole thing back or to provide you free of charge with whatever wasn't disclosed up front. In this case, it would be the number of "thangles" you need to complete your project. Of course, this would be a one-time deal.
Thus, you've put the ball back in her court...you've given her the opportunity to keep you as a customer (and it sounds as if you're one of her 'bread and butter' customers) or lose you as a customer. It's her move.
Now this is that "gremlin" in me speaking...the ideal time to do this would be when other customers are in the store...and could hear your conversation.
If all else fails, you could just leave the kit on the counter, walk out, and "eat" the cost of the kit, considering it a "tuition" charge to the school of learning to push back on merchants who do not respect their customers.
If this woman is smart, she will do whatever she can to make you happy, within reason, of course. She needs your dollars and your good will. It takes a long time for a good merchant to develop customers' good will. It can be deeply eroded within seconds. It seems to me that the owner of this quilt shop is dangerously close to losing the good will of a frequent customer.
As others have said, stay close to this board with both your questions and your enthusiasm and you will become a better quilter, enjoying it more. This is a world-class resource comprised of innumerable creative, smart folks.
Remember, it's your money and your time. You decide how you want to spend it.