New enemies spawn that have her other arm. They are larger and of higher level. (It could be you need to be a certain level before they spawn, but maybe it's only 50-100, not really sure.)
Was it a fox with one arm? I already have 2 right robotic arms before starting the part 2 of Inventor quest. Ah alright, I think I already broke the 2nd part of the quest. I starting over again.
