Ballerina Carla Fracci seems so much a part of the moonlit, disembodied world of romanticism she conjures on stage, it's hard for one to shake loose the spell long after the curtain is down. In the title role of "La Sylphide" at Kennedy Center Friday night, she surpassed, if that's possible, even her own elegaic refinement as Giselle, earlier in the week.

It was a loving, melancholy sprite she played, the agency but in no way the willing cause of thless as mortals come - gossamer light, unceasingly lyrihelss as mortals come - gossamer ligher, unceasingly lyrical, exquisitely phrased and shaded.

The American Ballet theater production of "La Sylphide," by the way, is holding up splendidly, showing the canny, sensitive hand of Erik Bruhn, who restaged it, at every turn. Marcos Paredes' portrayal of the vengeful crone. Madge, is nothing short of a tour de force. And though no one could duplicate Fracci's etherality, Cynthia Gregory's Sylphide on Saturday afternoon had its own distrinctive buoyancy. Ivan Nagy was dancing with restored technical brilliance, in partnering Fracci both in "La Sylphide" and the Sunday matinee's "Les Sylphides." Fracci's hands, wrists and fleet in the latter were a lesson in zephyrean fluency.

The rest of the weekend ABT performances I was able to catch highlighted novel or offbeat casting that really clicked. Rebecca Wright's spunky Cowgirl in "Rodeo" Saturday lit up the the whole ballet, with fine help from William Carter as the Champion Roper. The stylistic aptness of Leslie Browne, George de la Pena, Gayle Young, and especially Marie Johansson, helped revive the emotional impact of "Jardin Aux Lilas" yesterday.

Finally, Martine van Hamel and Clark Tippet took some liberties with the "Corsaire" pas de deux yesterday, but not without enchancing the manysided allure of their partnership.

At the Dance Construction company concert at WPA Saturday night, I especially liked the neurotic intensity of "For Verabelle," a duet by Maida Withers, and also John Bailey's "Crab Quiche," which plays satirical havoc with Pachelbel's "Canon in D." The affectionate spoofing of the '30s in "Put on the Music . . . Let's Dance!," an ambitious new group work, is somewhat overwhelmed by the memories it evokes. It has, however, passages of inspired lunacy.

The Washington Dance Theater gave the premier performance of Erika Thimey's "The Lamentations of Jeremiah," with music by Alberto Ginastera, at St. John's Episcopal Church in Georgetown yesterday morning. Despite limited means and space, the dance was both shapely and affecting.