HERE in the Lithuanian capital, in a small artists' colony just outside the city, the dying art of costume-making is staging a comeback.In the studio-home of Vanda Dudeniene one would never guess that this retired nurse has been weaving and sewing national costumes for only five years. Her wool, linen, and cotton fabrics are of the highest quality; demand for the finished product - complete national costumes consisting of skirt, blouse, apron, sash, and cap - is greater than what she can produce. But Mrs. Dudeniene says she would rather do the job right than get rich with a mass-production setup. It takes her between a month and six week s to complete one costume, for which she asks $150. She says she's never sold one in the United States, but she's heard she could make between $200 and $300 for one there. The money, however, is not what drives her. "It's too difficult to do it just for the business," she says. "I don't even want to sell all the costumes I make. When that much work and soul are put into your work, sometimes it's too hard to sell." Weaving was always something that interested her, but she waited until she quit nursing to take it up. She studied under the master weaver Klementina Gudonyte, who had graduated from a special crafts school in prewar independent Lithuania and whose work is displayed in museums. Even before Lithuania's 1940 annexation into the Soviet Union, which sought to suppress national identity, costume-making was becoming a rare craft. In their 1978 book "Lithuanian National Costume," Antanas and Anastasia Tamosaitis expressed the fear that the advent of factory-made cloth would hasten the passing of costume-making as a creative folk art: "By the early twentieth century," they wrote, "hand-woven holiday clothes had become national treasures cherished as museum pieces and collectors' items." Under the inefficient communist system, simply getting set up and keeping a store of supplies was as difficult as the threat posed by mass-produced cloth. Dudeniene's neighbor, an engineer, built her looms. She gets her supplies through an association of folk artists, which also helps her sell her wares at exhibits in Lithuania and abroad. Some of the dyes she makes herself, such as grays and browns that come from oak tree bark. As Lithuania's national identity revives, demand for costumes has increased. "Before, people restricted themselves from buying, because there was no chance to wear national costumes," says Dudeniene. Her daughter, Aurelia Skeiriene, the secretary to the mayor of Vilnius, says "It began to change on March 11, 1990 (when Lithuania declared independence). After that date, we felt Lithuanian for the first time." Mrs. Skeiriene recently saw some Canadian Lithuanians in "native dress but they "weren't genuine," she says indignantly. "They were deeply stylized. The colors looked like neon." She models one of her mother's creations, a billowy, colorful combination that inspires her to demonstrate a few dance steps. Young people have a growing interest in costume-making, says Dudeniene. But it looks as if the tradition won't be passed to her own daughter, who says she has no plans to take up this painstaking work. "I'm too lazy!" she smiles.