omg it just hit me that Maria probably chose to sacrifice herself like that because she knew she was dying any way, and knew she wouldn't have been able to survive Earth without the Arc's technology, and Shadow would have had to watch her die regardless of the raid or not, so she probably figured that Shadow would actually have a fighting chance if she saved him first.
I like to think Maria had days stuck inside her head sometimes. She's naturally a positive person, it seems, but I like to think her thoughts could get dark. She's in pain, probably agonizing at times. It's hard. It's debilitating. They're not any closer to finding a cure. She wants to give up on really bad days. She hates that Shadow has all this pressure to be her savior, pressure she never puts on him.
Her body struggles with ARK-tech. Tech currently unavailable down on her beloved planet. It has an atmosphere that she can't thrive in.
She knows she's not going to make it to Earth.
But Shadow gives her hope, that maybe. Because she's always given him hope that he could be more than what he was created for, so he gives her hope that she's bigger than her diagnosis.
And she was. She was brave. She was strong. She loved her weird alien brother so much that she herself probably loaded a most-likely weakened Shadow into a pod, and put herself in front of a loaded gun to save him.
She knew she wasn't going to make it to Earth.
