User blog comment:Gundam Legilis/Beginning Of The End In Depth/@comment-24.93.195.246-20160106165931

Pyrrha was feeling the metal of the weapons on his boots most likely, never elaborated.

Plus Yang's fist was covered in her gauntlet, and barely "touched" Mercury's leg for a fraction of  second, plus with the high of adrenaline it would not be surprising if she didn't realize it was a prostetic.

And that is not even considering Emerald's halluncination ability.