She sold her pins to people she knew. Friends, family, friends of friends were her best customers. It was inevitable that one of them would take a good look at those pins and want to learn how to make them. This is true of any popular craft. There wouldn't have been a problem.
Painting requires some talent.
Most people can't paint, but most people CAN flatten a circle of clay and stick it on a pin back. All over the craft world were people making things that required glue guns and lace, and not much talent, then selling them for profits of ten times their cost to produce them. Customers became tired of seeing all that ruffled polyester blue and mauve stuff on the majority of tables at every show. The people who spent the most money on handmade items became more discriminating, and those who still had a stomach for it learned to make things themselves.