The Sweater Girl is back. She looks nothing like the Lana Turner tight-sweater, pinup variety. The 1983 model, who likes easy-fitting sweaters of all lengths for both daytime and evening, got a big boost from an assortment of designers today, the final day of the New York fall shows.

Perry Ellis' strong suit has long been sweaters--the hand-knit, nubby variety that his young and rich customers love to wear. He started the rage for sweaters with the cable down the center. This year his best sweaters are patterned like zebras and tigers, both for men and women, and they are bound for huge success both at his high prices and in cheaper copies. One version is an update of the sweater set: a zebra-printed coat-like sweater with a matching shorter pullover. Ellis also showed an update of the Fair Isle sweater--in fur--for both men and women. In addition, Gloria Sachs' sweaters are some of the best of the season. Her customers, like Sachs herself, are successful businesswomen, and her handsomely colored cashmere, mohair and angora sweaters, keyed to subdued patterns in skirts or pants, prove appropriate. "She has a sense of what real women want to look like," said Marilyn Kaplan, a Neiman-Marcus vice president, after the show. "The clothes are timeless and modern."

Sachs' short, black-cabled sweater-jackets will solve the problem for women who are reluctant to wear a revealing sweater to the office. And her long cashmere sweaters with silk skirts will be one way elegant women will want to dress for dinner next fall.

Meanwhile, for Halston fans, the designer who always offers cashmere sweaters and ponchos has added the dimension of sweaters with intarsias, inlaid patterns, which this season for Halston are poppies. He gets a sweatery look, as well, in many of his evening clothes done in chenille, a velvet-like yarn usually thought of for bathrobes and bedspreads but an old classic that feels cozy.

The first clue that Michaele Vollbracht, the master of painted silks, was off on a new tack was his young employes in fuzzy striped sweaters checking in guests for the show. "This collection is odd," Vollbracht wrote in his hand-scrawled press release. "First because I enjoyed doing it--second, because it gave me freedom from the brush. I am certainly not biting my hand that feeds me--just dodging a label." Vollbracht has translated his design talent remarkably from paint to print, with patterns, for example, that look like real feathers but are printed. And his sweaters in uncommon textured wool combinations and shapes are among the best of his new designs.

The sweater revival is obviously tied to the overall slim though not tight look this season, and the return of a kind of clothing that has been out of the fashion spotlight for years. But sweaters are not all that these designers are doing. Sachs, for example, puts many superb easy coats over her clothes, always with width at the shoulder, and frequently in the most luxurious of all coat fabrics, alpaca.

Ellis has developed his popular theme of last season--the waistline cinched with nine-inch-wide belts--with skirts and pants that give the same effect. By raising the waistline on his pants and skirts, he achieves the same tight torso silhouette. The skirts are usually long, almost to the ankle, and made full with pleats or gores, and the pants are pegged to the hem. With them he has put short, flyaway jackets that barely cover the bust.

"There's a young customer, and even one not so young, who will wear Perry's clothes whatever he does," says Joan Kaner, fashion director for Bergdorf-Goodman. "They loved his clothes even when the clothes make them look twice their size. They'll love them particularly this year."