Bernarda's behavior toward her daughters is abusive, even in the context of the time in which Garcia Lorca's drama takes place. She seems not to care or even to recognize that by keeping the girls under lock and key, she's depriving them of basic human needs. Adela is the one who rebels most fully against the mother's dominance by having a relationship with a man, Pepe, albeit covertly.
In doing this Adela is in conflict with not only her mother but her sisters as well. Angustias, the oldest daughter, is the one the young man is supposed to marry, and at least one of the other girls is interested in Pepe as well. The situation in the household is the proverbial powder-keg set to explode. Since Adela is the one who asserts herself, she's the one who actually pays the price for her rebellion, but by her own hand: she kills herself when she assumes that Pepe has been killed.
It would be facile to say that Adela represents feminism. The setting is one in which conditions are so backward and hopeless with respect to gender issues that Adela's actions unfortunately, and tragically, misfire, and she ends up destroying herself. But at least she has tried to make her own life, so to speak, and her self-assertion is, in fact, a statement in favor of not just women's rights, but human rights. The tragic irony of the play is that it is a woman, Bernarda, who is herself cruelly victimizing other women.