We don't actually know too much about the speaker of "Power." We can be sure that she reads about Marie Curie (in a book or magazine, perhaps), but we cant be sure of much else. Because Adrienne Rich is known for writing pretty autobiographical poetry, we have gone ahead and called the speaker "she" throughout this study guide. But we can't assume that Rich is the speaker because she's never said as much.
The one other thing that we can say about the speaker for sure is that Marie Curie's death has had an impact on her. She feels moved by Curie's story, by the ironic tragedy of her death—that science was the root of her power, and her eventual undoing. And she's moved by the fact that Curie denied this until the end.
Given that this poem is definitely a product of the women's movement, we might take a few stabs at what it is about Curie's story that has our speaker so moved. Curie was a pioneer as a female scientist, and yet she also denied the cause of her death. We can't ever know why, but it might just be that Curie didn't want to show the downside of her work, because it would endanger her status as a scientist, and it might put her discoveries at risk. In that sense, she's between a rock and a hard place as a woman, as a scientist, and as a pioneer in her field.
Does the speaker identify with Curie? Perhaps she looks up to her? The poem doesn't definitively comment on this, but we feel pretty comfortable saying that the speaker empathizes with Curie's life story, and maybe she feels similarly about the choices she's made in her life.