When we first meet her, we find out much about her anxieties and fears.
She fears loss, she fears loneliness and being once again left behind. She fears becoming a burden to others, of not being able to help other people, that if she is a burden she will be left behind, to the point where she's willing to feign not feeling pain from her Oripathy:
The Doctor promises that they'll never leave her behind, and for a happy few years, they make good on that promise. Amiya spends several joyous years with Kal'tsit and Theresa and the Doctor, until one day, the Doctor reneges on that promise, the tower crumbles, and it all comes falling apart.
The thing that gets me most about this is that, Amiya, who is too young to understand the vast conspiracy that she has been inadvertently caught up in, and who still harbors the doubts and fears about herself that she had in the past, thinks this is on her. She thinks that her inability to move or even scream means that there is more that she could have to help Theresa, that when Theresa plunges the blade into her, she deserves to feel its pain.
In the end, all of Amiya's worst fears have come true. The Doctor and Theresa are gone now and she let them down and it's her fault. In the end, everyone she cares about leaves her and she is once again alone.