A woman will pay anything for a dress she feels she can't live without," says designer Bill Blass. That's his explanation for the success of his most expensive dress this season. To date, he has sold more than 20 of the velvet, sable and taffeta style, right, with a price tag of $5,200 plus tax. The dress is cheaper if you choose mink instead of the sable.

Blass, who finds that many women are picking up the looser clothes because of their "childlike quality" and because "one feels so comfortable and relaxed" in them says it is essential that women to be offered an alternative. "Most affluent women don't want oversized clothes," Blass says. "They've worked too hard to get the figure slim. And the old man paying the bills wants her figure to show." Blass, who thinks fashion shows are still an unbeatable form of entertainment, presented his collection Thursday night at Lord & Taylor's Chevy Chase store for the benefit of the Corcoran Gallery.

Jacqueline Onassis, a regular customer of designer Emanuel Ungaro, skipped the opening of his New York boutique Wednesday, but called for a private appointment with the designer. So did her sister, Lee Radzilwill. But first on line with purchases at the new Madison Avenue store were Doris Duke, Babe Paley, Lauren Bacall, Princess Yasmin Khan and others. "It is necessary to have a shop in New York so people can understand the whole range of designs." Ungaro explained.The "range" includes accessories and furniture, as well as French clothes, couture as well as ready-to-wear, such as the fall dress at left.

Henri Bendel president Geraldine Stutz, center, a member of the National Council for the Arts (itself under the umbrella of the National Endowment for the Arts) representing fashion, has proposed a task force to produce recommendations and guidelines for a fashion program within the Endowment, under the aegis of Architecture and Environment Arts and Roy Knight.

"Fashion may not be free-standing art - but it offers credentials which can hopefully, earn it at least handperson status among the disciplines of the Endowment," Stutz told the council. "There are a great many talented people - and a number of first-rate atists - who use fashion as their medium. Their work with shape, technique and color transcends craft - and rates recognition and support."

Picking up on the theme of the late James Laver, curator of London's Victoria and Albert Museum, who insisted that everything about a period could be learned from a study of its clothes, Stuzt concluded, "In our present search for a recovery of national pride - and our growing interest in our national and regional heritage - museums could offer a marvelous, fresh and valid view of our history through fashion."

Kenneth Jay Lane, costume jewelry designer, never had to go beyond his own living room, packed with bibelots including ivory figures, memento mori (including 17th century English mourning rings), boxes and clocks, to find ideas for his designs. But now he's giving up his townhouse and all the collections, including a group of Indian miniatures he never found wall space to hang. "The house is too big, the wife moved away, there are two empty floors, so I'm moving to an efficiency," says Lane, who admits also that "Times are not that bright. Costume jewelry is not the rage it was 10 years ago."

But times are not so bad, either. He's designing pearls, particularly the big 30-inch waist-length baroque variety, crystal and porcelain jewelry, watches, handbags, slippers and what he calls "fake KLJ" copies of his costume jewelry in real gold and diamonds.

Lane plans to keep most of his Boulle furniture "because it is the simplest thing to have," sculptures weighing over one ton and some pictures four feet tall, when he moves to an "efficiency" - one with a balcony and 18-foot ceilings - in a Stanford-White-designed house near his present Manhattan home.

Does Tiffany's tell Blooming dale's? The posh 57 th Street shop told the big department store in a New York Times ad that mesh jewelry, promoted by Bloomies from the Givenchy collection, was in their Elsa Peretti jewelry collection two years ago. Bloomingdale's responded, tracing mesh jewelry back to 3d century Denmark, and claiming a Peretti connection back to 1971.