Because you can't tell me Leia didn't have a moment where she just broke down. Shortly after ANH, Leia POV
The second morning After Leia wakes up, and for a moment she doesn't remember.
She wakes up slowly. The room is hotter than she is used to, she thinks dimly, maybe she should ask Annai, her handmaiden, too open a window. And why is it so loud? There aren't usually so many voices to be heard in Leia's room.
She opens her eyes. And suddenly she remembers. In that moment, it is as if a huge wave crashes over her and pulls her under, and for a few moments she feels like she's drowning. Leia's not a fan of such poetic rhetoric, has never been, she prefers practical, clear speech, but right then... it's the best way to describe it. The sheer intensity of both her anger and her grief hits her like a punch in the gut, only it doesn't stop. Everything hurts, and gods, she was tortured not three days ago, and she feels it again, she feels every single one of her bones, and she can't move, and some distant part of her brain realizes that she is going into a panic attack, but there is nothing she can do, no way to stop it.
When she finally stops seeing Alderaan exploding and interrogation droids, she is shaking and sobbing and she wants nothing more than to curl in a ball and die, so that she might meet mama and papa again in the afterworld, where Alderaan is whole and nothing hurts and where she can believe that everything will be alright. In this moment she wants to hate Luke and Han for rescuing her, for not letting her die when her whole life had already ended.
But she can't, because Leia's parents raised a strong young woman, and she remembers them too well to believe that they would support her decision to end her life, because it would feel like betraying them and everything they fought for to give up.
So she stands up. Her legs are weak, hardly carrying her, and she still feels every bone in her body, but she goes to the fresher. The clock shows lunchtime, which means that she probably lay in her bed sobbing for a few hours, and when she looks into the mirror, she can see it, sees her red swollen eyes and the dark rings under her eyes and the hopeless look on her face. But she also sees the necklace she's wearing, a present from her mother for her sixteenth life day, and in that moment she promises herself to continue fighting. Her life might have ended, and she might end up destroying herself, but she'll be damned if she doesn't at least try to take the Empire with her. She owes that to her parents, to the whole planet of Alderaan.