Ballerina Carla Fracci, who'll be returning to Kennedy Center Tuesday as a guest artist with American Ballet Theater after an absence of more than five years, is as much of an enchantress as the fey heroines she so often portrays.

Her performances of such roles as Giselle, Swanilda in "Coppelia," or the fugitive sylph in "La Syphide," remain among the most memorable classical interpretations of our era. (She'll be recreating all three parts during ABT's coming three-week series here.)

She's married to stage director Beppe Menegatti, to whom she attributes much of her own sense of dramatic projection. But the aura of theater surrounds her like a halo, as something in her nature, something given in the fiber of her being. Dark of hair and eye, her beautifully molded features quick and mobile, she speaks in private conversation with the same luminous animation she conveys from the stage, gesticulating with hands, brows and mouth but always centering her gaze directly, attentively, intensely at her interlocutor.

Despite this sufficiency of magnetism, and the distinctness of her presence on stage, in speaking of her art it is always on an interaction with others that she seems to dwell.

"I hate to be alone," she said the other day during our interview, unconsciously inverting the Garbo formular. She meant during a performance, in the midst of a dramatic evocation, but one suspects her need for interpersonal exchange doesn't stop when the curtain comes down.

Perhaps that's why so many ballet devotees almost invariably think of Fracci in conjunction with Erik Bruhn, the great Danish danseur noble whose landmark partnership with her began in the early '60s and ended here in Washington in 1971. It was the crucial experience of her artistic career, terminated only by the illness which forced Bruhn's abrupt and unexpected, if temporary, retirement from performance.

"I am a person," she says, "and I remain a person in the theater, on the stage. I feel that I must know the people I am working with, dancing with, in order to make a performance real and true.But it takes time to get to know someone, time for conversation, understanding, time that a dancer's life, with its incessant practice and rehearsal, doesn't often permit.

"But sometimes the knowing happens anyway. It was a special thing with Bruhn, it was natural, we didn't need to talk, to explain, to do anything. We just understood each other. I think that's why our performances of 'Giselle,' for instance - we did it so many times together - were always so alive. I don't say it got better each time, that's not possible even though one strives for it, but the life spark was always there."

Bruhn has the same feeling about the collaboration. In a recent interview, he said there is "nothing to compare with Caria . . . We thought together, breathed together. We could laugh with each other, at each other . . . When we danced together, we felt as if we were alone. Just by ourselves. It was magic."

"Yes," Carla agrees, "it really was magic. People often come away from a performance saying, oh, that was special tonight, I wonder what it was that made it so wonderful. With Erik and me, we could build a whole performance from a little detail, a look that passed between us, a touch of the hand, because of this deep intuitive understanding we had. It was love on stage, in a way."

Ironically, Bruhn also will be appearing with ABT during the coming Kennedy Center engagement, not in the romantic leads of his earlier career, but in the character roles - the eccentric dollmaker in "Coppelia," the evil witch in "La Sylphide" - he has been assuming since his return to the theater in 1975.

Fracci will be partnered in "Giselle" on opening night by Ivan Nagy, by Ted Kivitt in "Coppelia," and by Nagy again in "La Sylphide." She has already danced with these ABT principals and has nothing but praise for their work, bu she admits to an eerie twinge, particularly in the case of "La Sylphide." This was the last ballet she and Bruhn danced together, at the Kennedy Center in December of 1971, before his sudden retirement.

"I danced it again this past January in New York with Nagy as James," she recalls. "Bruhn was also in the cast, as Madge with Witch, and I must say, I felt a little, well, embarrassed by it. It was very strange. But he was very happy and relaxed. He loved doing the role, and he does it so fantastically well. All the same, every time I dance the Sylphide, I cannot help thinking of Erik dancing James. He's always with me in this ballet."

Though she is known especially, particularly in this country, for the romatic roles of the 19th century, her repertoire is vast in size and stylistic reach. John Butler, who choreographed "Medea" specially for her and Mikhail Baryshnikov, more recently created on "Othello" for her, to music by Dvorak. She's done Antony Tudor's "Lilac Garden" and his "Romeo and Juliet." Maurice Bejart, Glan Tetley and Lar Lubovitch are devising roles for her currently. SHe cherishes the diversity. "I feel enriched by the diversity of parts. When I return to the classics, I feel I an revivified, and have more to offer in the old roles," she says.

But more than anything else, it is the constant changing of partners, inevitable in today's ballet world, that enables her to resurrect a sense of freshness and spontaneity in performing the same role evening after evening, season after season.

"Each partner is so different. It's not just a matter of their styles, or technical idiosyncracies, not just that this one does an arabesque this way, and that one another way. It is the change of feeling, of rapport. Each one gives you something of himself, something personal and new to you, and you react in a new way - this is what charges my performance again with life." This appears to be Fracci's artistic credo - providing the emotional chemistry is favorable, one plus one make a great deal more than two.