For more than 18 months, Lin Cheng, a Taiwan native, toiled over a small sewing machine in an upstairs room over an elegant women's boutique in Old Town Alexandria.

There she and 32 other seamstresses could earn the minimum wage or get paid piecemeal rates, typically earning $35 to $50 each for garments that would sell downstairs for $500.

Then last April Clarissa Brainard, owner of the small store which bears her first name, announced she was cutting the rates she paid for piecemeall work. On one popular item alone, an ultrasuede coat, the fee dropped from $50 to $35.

That was too much for Cheng, a naturalized American, who attempted to organize a protest of her fellow workers and suddenly found herself fired because Brainard called her "a slower worker and troublemaker."

Undaunted, Cheng decided to fight. This week in a little-noticed proceeding before the National Labor Relations Board, she won.

"I won an American right," the 31-year-old woman said proudly. "I wanted to show after I was fired that you can do something about what happens to you."

Just before her complaint against Clarissa Inc. was to come before an NLRB panel, the company agreed without admitting wrongdoing to meet Cheng's demands. The settlement means Cheng will get $550 in back pay and that Clarissa will have to post an unusual notice among the scarves, coats and costly knickknacks in its downstairs shop. The sign willl say that the workers there have a right to organize.

The victory, says Christopher Hodge, the third-year student at Washington's Antioch School of Law -- who represented Cheng before the agency, is all the more symbolic for where it occurred.

"Her case is typical of how an employer in Virginia, a state that is hostile to unions, is able to prevent people from organizing," he said. "You fire one employe as an example to others."

Brainard, 52, who started her apparel business in the basement of her house disagreed. "I settled because I was tired of the hassle. The women who work here like it and if they have problems they can come to me. They don't need a union here," she said.

According to Louis D'Amico, acting director of an NLRB regional office, the matter is unusual precisely because of a complaint was made "there are hundreds, maybe thousands of situations like this that never get brought to our attention. Obviously we can't act unless we find out about them. In this case, the office thought there was merit to her complaint," he said.

"The working conditions at Clarissa's are not bad, but . . ." said Hodge, 29. "Look at the difference in price between the $50 or so they were paid for sewing a coat, and the $500 tag. She was well within her rights to want to band together with the others to protect herself," Hodge said.

Brainard sees things differently. "We specialize in Ultrasuede," a washable artificial fabric with the feel of leather or suede, she said. "The material now costs $25 a yard and each coat needs three to four yards. When you add the cost of buttons, zippers, trimmings and labor, you've got closee to another $100. The overhead for working here is high, and the trucking company is going to raise its rates again, for shipping the garments across the country. We're not stealing any money," she said.

Brainard pulled out her computer-printed payroll logs to show that some of her 32 employes who use 13 sewing machines gross as much as $1,772 each month. "I only earn $2,000 a month," she said.

Brinard and Cheng see most matters in radically different lights. "That woman [Cheng] liked to talk, talk, talk," Brainard said, moving her hands in the action of a mouth. "Once she stepped on a Ultrasuede bedspread we were making." The bedspread retails for $3,340.

Cheng, however, said that "jealousy" on part of Brainard toward her when she began to organize the other women led to her firing. From the start of her employment on Dec. 12, 1977, to her firing on April 27, 1979, "I was told I was a good employee." She said that her take-home pay during her last month of work was about $600.

She said she did not insist on being rehired "because I don't want to go back there."