Wrong. Here are some counterexamples:
Adriana Hölszky, Allison Cameron, Amy Beach, Annea Lockwood, Annette Schlünz, Annie Gosfield, Barbara Benary, Barbara Strozzi, Bianca Maria Meda, Carla Bley, Carla Kihlstedt, Caroline Shaw, Cecile Chaminade, Charlotte Moorman, Chaya Czernowin, Chen Yi, Clara Schumann, Cécile Charminade, Daphne Oram, Delia Derbyshire, Diamanda Galás, Dobrinka Tabakova, Edith Canat De Chizy, Elena Kats-Chernin, Elena Mendoza, Eliane Radigue, Eliza Brown, Élizabeth-Claude Jacquet de la Guerre, Elizabeth Lutyens, Elizabeth Maconchy, Ellen Fullman, Ellen Taaffe Zwilich, Elodie Lauten, Ethel Smyth, Eve Beglarian, Fanny Mendelssohn, Florence Price, Frances-Marie Uitti, Francesca Caccini, Gabriela Lena Frank, Galina Ustvolskaya, Germaine Tailleferre, Gloria Coates, Grażyna Bacewicz, Ha-Yang Kim, Haco, Helena Tulve, Hildegard von Bingen, Ikue Mori, Isabel Mundry, Isabella Leonarda, Janice Giteck, Jennifer Walshe, Jenny Scheinman, Jessica Pavone, Jin Hi Kim, Joan La Barbara, Joan Tower, Johanna M. Beyer, Johanna Müller-Hermann, Judith Weir, Julia Wolfe, Kaffe Matthews, Kaija Saariaho, Kassia, Kate Moore, Lera Auerbach, Libby Larsen, Lili Boulanger, Liza Lim, Lois V Vierk, Louise Farrenc, Louise Talma, Maja Ratkje, Margaret Bonds, Maria Schneider, Maria Szymanowska, Marian Zazeela, Mary Halvorson, Mary Lou Williams, Maryanne Amacher, Matana Roberts, Meredith Monk, Michiyo Yagi, Miya Masaoka, Nadia Boulanger, Nina Senk, Okkyung Lee, Olga Neuwirth, Pamela Z, Pauline Oliveros, Peggy Glanville-Hicks, Rebecca Clarke, Rebecca Saunders, Regina Carter, Rosa Giacinta Badalla, Ruth Crawford Seeger, Sachiko M, Sainkho Namtchylakv, Sarah Kirkland Snider, Satoko Fujii, Sheila Silver, Sofia Gubaidulina, Sofia Jernberg, Susie Ibarra, Thea Musgrave, Theresa Wong, Unsuk Chin, Vanessa Lann, Vítězslava Kaprálová, Wendy Carlos, Wu Fei, Wu Man, Yoko Ono, Zeena Parkins, the list could go on...
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