Twilight took a step back from Dark Pit. She hadn't expected him to start shouting like that, and she really wasn't considering all the innocent lives he mentioned. She had her own world's best interest in mind, but she couldn't live with herself if she saved her little ponies while at the same time screwing over every other creature in this dimension. Plus there was the fact that Equus would be endangered whether she helped Dark Pit and Meta Knight or not. Twilight was still angry at the two for endangering Equus as a means to get her on their side, but there was no point in backing out. That would just mean more lives lost.