Alegría was born in Estelí, Nicaragua and grew up in the Santa Ana area in western El Salvador. In 1943, she moved to the United States and in 1948 received a B.A. in Philosophy and Letters from George Washington University. Alegría was committed to nonviolent resistance. She had a close association with the Sandinista National Liberation Front (FSLN), which overthrew Anastasio Somoza Debayle and took control of the Nicaraguan government in 1979. Alegría returned to Nicaragua in 1985 to aid in the reconstruction of Nicaragua.

Alegría now lives in Managua, Nicaragua.

Alegría's works of literature reflect the style of the popular literary current in Central America during the 1950s and 1960s, "la generacion comprometida" (the committed generation). Her works follow the practice of several poets of her generation who are critical of their societies and make claims for rights using a language which is often counter-literary. Alegría has published many books of poetry: Casting Off (2003), Sorrow (1999), Umbrales (1996), Fuga de Canto Grande (1992) and La Mujer del Río (1989).

Alegría has published novels and children's stories.