Gilje was born in Bay Ridge, Brooklyn. She received her BFA from the City College of New York and trained as a conservator from 1967 to 1971 at the Museo di Capodimonte in Naples, Italy. Gilje apprenticed in Rome with the restorer of antique paintings, Antonio deMata, from 1966 to 1968, Gilje continued her apprenticeship from 1968 to 1972 at the Museum of Capodimonte in Naples.
In 1973, she returned to New York and worked in the conservation studio of Marco Grassi, where she restored Old Master paintings for private and museum clients, including Stanley Moss, E.V. Thaw, Robert Dance, the Metropolitan Museum of Art in New York, the Norton Simon Collection in Pasadena, and the Thyssen Bornemizsa Collection. In 1976, she opened her own studio. During this period she also created artistic works, initially relief sculpture and then painting which was exhibited in various SoHo galleries. Gilje began to combine her knowledge of conservation with her own painting creations in the early 1990s.
In her paintings, drawings and installations, Gilje applies an art historical analysis and uses methodologies of conservation to create altered versions of familiar paintings which suggest alternative interpretations of the original artworks. In this way she encourages her audience to think about a work of art on several levels: its material and historical narrative. An example of this is Rembrandt’s Danaë defaced by a vandal with acid in the Hermitage, its contemporary symbolism translated into up-to-date equivalents; another is Caravaggio’s Boy Bitten by a Lizard, Restored,1992, where the lizard is replaced by a syringe, suggesting a link to the risk of AIDS.
Many of her paintings engage feminist issues, although they are sometimes controversial (as in her series of "Sargent's Women," portraying 48 women visually excised from paintings by John Singer Sargent, all rendered without their luxurious clothing). In Susanna and the Elders, Restored, 1998, Gilje exhibits a recreation of Artemisia Gentileschi’s Susanna and the Elders (a story of sexual abuse) hanging next to an x-ray of the painting. When Gilje recreated Gentileschi’s painting, she made an underpainting in lead white (lead white x-rays well) of Gentileschi’s own rape by Agostino Tassi. In the x-ray we see Gentileschi’s arm extended holding a knife in self-defense and her face contorted and screaming. The image can faintly be seen in the pentimento as well. Her references can be provocative as she addresses timely social, political and personal concerns.
Gilje create a number of portraits in which her subjects were placed in the context of an historic painting of their choice; these were displayed in her exhibition Curators and Connoisseur at Francis M. Naumann Fine Art, New York, in 2006. For example, art historian Linda Nochlin chose Édouard Manet’s 1882 Bar at the Folies Bergère for Gilje’s Linda Nochlin at the Bar at the Folies Bergere, 2006, and art historian Robert Rosenblum chose Ingres’ 1823/26 Comte de Pastoret for his Gilje portrait of 2005.
Over the course of the past twenty years, her work has been shown in various exhibitions throughout the United States and in Europe. Several critics and art historians have written about her work, including Robert Rosenblum, Linda Nochlin and John Yau.
Gilje is represented by galleries in New York, and her work is in the collection of several museums, including the Weatherspoon Museum, University of North Carolina, Greensboro, NC, National Museum of Women in the Arts, Washington, D.C., Yale University Art Gallery, New Haven, CT, The National Portrait Gallery, Smithsonian Institution, Washington, D.C., and the Williams College Museum of Art, Williamstown, Massachusetts.