I am so sorry you ran into this. But I'm afraid that snobs are everywhere. Shame on her. I don't care that the price for her commission was included in the "dealer price", isn't it always? Geeish. Instead of pittying the commission she lost by you buying another machine, she should have thanked her stars that you wanted to learn more and were willing to ask her. And some wonder why their sales drag? Who wants to buy from a pity party?
Find someone else that teach you the techniques you want. Check out the LQS for possible guilds that might give you
more support. When our guild workshops come around, you can see a gammut of sewing machines in the room. We Feather Weights, I take my Singer 301, someone else has the to the nines computer machine, and all the types in between. The machine can have a great bearing on how the sewist sews, but by and large it is the operator that has the most control. You can make beautiful things with the simplist machine.
I've got to step off the soap box now before it becomes a stage!!!