Shepard has always hated the stars. They make her feel small. They make her feel angry.
She knows it's silly and irrational to hate them as much as she does, but silly and irrational has never stopped her before.
For millions of years, the stars in the heavens—the same stars that many, many races have seen—have just watched. They have only watched as their dependent races rise and fall; they have watched the Reapers carve destruction into their worlds a thousand times over. Through all this, all they do is burn. All they do is burn, waiting for a new set of species to begin life anew in their systems. When that life is young, they shine there, glittering, charming all they can into coming up and out into the cosmos to greet them. When that life finally gets to meet these gaseous succubae, it seems only an instant before they collapse under the weight of an ancient, once unavoidable, evil. And the stars just watch.
Shepard could never say what she wanted them to do, but she knows she wants them to do something. Anything.
Alchera. Dying. She was left flailing helplessly in the vacuum, reaching out to those pinpricks of light in desperation. But they just watched. She cried out for help, expecting a miracle from those lights. Certainly, with all that she had done for this galaxy, for its people, she deserved a helping hand—just this once. No miracle came that day. They all sat, billions of miles away, twinkling. Apathy, or derision? She couldn't tell. Too soon had her vision hazed into black, and her body fell through atmosphere. The last things she saw clearly were the stars. She still hates them for it.
Cerberus decided it was a good idea to add expansive windows, and one conspicuously placed skylight, to the Normandy SR-2. From the comfort of her own ship, she is now able to watch the stars and their constant, infuriating, ignorance. When the Collectors were attacking, the galaxy was bright and shining. Nothing was out of place to those stars, even if the people they gave life to were being harvested for an unforgivable cause. When the Reapers struck the colonies and homeworlds soon after, the stars did nothing to help their people. They only continued to shine and burn, ignoring the pleading eyes as they had all the rest.
She knows what stars really are. She isn't stupid. They are really insentient, unfeeling, ancient balls of gas that burn themselves up from the inside, only to later be replaced by new insentient, unfeeling balls of gas. They are not gods. They don't have any magical cosmic powers and they certainly do not grant wishes. They're just powerful, suicidal forces of nature.
But Shepard can't accept that fact. She won't accept that fact. She is a, tiny, singular human being in a universe more vast than conscious thought can begin to fathom. So far, in her short (two) lives, she has done so much for this galaxy—whether anyone chooses to admit it or not. She has cried, bled, and lost for the sake of the worlds and people orbiting those powerful, distant stars. It is only fair that she wants the stars to help, and she wants them to be alive. She needs them to be alive. She needs them to care. To feel. To take responsibility. The Savior of the Galaxy is a fancy title, but even she needs someone—something—to blame.