Mucho texto....
Nepht was happy because she could use her strength to attack Accelerator without killing him and the reflection was fracturing her so she was reflecting a force greater than her durability ergo she was hitting him very seriously.
Seriously, people start to take out everything to say that everything is "peak human", I think many people will start saying somethings like "Wonder Woman is damaged by bullets" or that "Thanos was taken prisoner by normal policemen" as a serious argument.