Diferença entre "Open" e "Get it open"
"Vou abrí-la!" o "get it open" acredito que seja para dar ênfase na ação que o personagem x vai realizar em virtude de soltar o companheiro.
Plus, with "I will get it open", somehow, means that the character has made a decision on the spot. As opposed to a planned or arranged decision. That would fall into the topic category of "I will" vs "I am going to". That kind of use is usual in English.