““Nothing she can’t do outside the bubble that she couldn’t do inside,” Tattletale replied.” Triple negatives and incomplete sentences are hard to parse, but I think it works as dialogue. Just don’t think about it too hard.
Yeah, the technical meaning is almost certainly not what she meant (there isn’t anything she is unable do do outside the bubble that she is unable to do inside, meaning that anything she can’t do inside, she can do outside), but it’s a realistic error that’s just as easily pinned on Tattle as on Wildbow.