Sorry to hear of your awful experience. One would think a shop owner would quit stuffing her face long enough to assist a potential client.
I dress in jeans and nice t shirts most of the time. I have had store employees look down their noses at me. And when looking around I have had then say, the "clearance area" is in back. "I go how nice is that where you got those rags your wearing then".
Just smile and say, "I shall take my business elsewhere, where my money is appreciated. And where they know how to treat people."
When we first moved here, my husband owned a red pickup truck. During nice weather, I drive around with the windows down and I like to listen to the stereo. As I was walking into the local salon, my daughter was going to having her hair done. I overheard a lady talking to another woman about me. She said there was a new family in town and the woman drives around blasting that awful rock and roll music. I turned the corner and said..it was Metallica and I would appreciate not being the topic of beauty parlor gossip queens.
They sat there with their mouths hanging open.