Amy got very bashful (or "felt very bashful" or "became very bashful"); she already knew that her father had contributed to make that possible, the war against the trolls. Just because they didn’t accept that trolls were people and that they had a heart and were capable of loving as much as humans were!
“I know,” she said, so quietly that the troll could barely hear her. "And I am so sorry, for everything, for your lost (or "your losses" or "your lost kin/citizens/soldiers"), for your pain, for the war… I am very sorry!”
Something inside the troll was touched by her words, but at the same time his revenge and fury were stronger.
“For the last time, go away if you don’t want me to smash you like a bu!!" (?) said the troll furiously.
Amy was almost convinced that having come here for help was a mistake, but her need was so huge that she decided to apply her plan B. She swallowed and inhaled deeply to calm her nervousness (or "to calm her nerves") before talking again.
“I know you are angry, upset, heart broken, sad and a lot of other upset feelings. I also know you hate this place and you would like to be with someone who understands you…I mean, more trolls. If you help me, I can help you to go (or "reunite") with your people,” said Amy with a slightly trembling voice, but with the confidence that she was going to be able to convince the troll to accept help. Despite his anger, the troll found a little hope in her voice, because she was right. He hated this place that just provoked pain in his soul -- and, yes, he had a soul, although people thought otherwise. He knew that there was a place where only trolls lived, where he could feel understood and accepted. Trying to hide his curiosity, with a bitter voice he asked, “How could a simple kid offer such an audacious thing to a mighty troll like me?" He didn't look at the girl.
"bu"? Did you mean "like a bull"?
Alternative: "Amy was almost convinced that coming here for help had been a mistake"