How did you think it went when vriska was getting the arm from equius?

This is actually answered in the second Paradox Space book, in the story Vrisky Business, which in its full form exists only on paper. I haven’t read it, personally, mostly because I dislike paper books, but based on the preview, it seems that she just walked over to his house, collapsed on the floor, and Equius, being at heart a compassionate individual (though it’s often very difficult to tell through his extensive conditioning into Alternian values) fixed her up.