Were the peonies regular herbaceous or Itoh? I wouldn't dig anything up, would look to see if an roots were displaced and cover them if they were, firming them down to make sure there were no air pockets introduced. Did she yank up all of the stems? Impossible to tell if there was enough damage done to kill the root but if she removed all it is possible. If the plant was an Itoh I'd at least try to replant the pieces, some people have reported that removed stems have rooted. Heck, I'd even try it if they were herbaceous, can't do even more damage. I wouldn't completely give up on the roots, some hybrid herbaceous have adventitious roots, will grow eyes on pieces of root left in the ground that had no eyes before. It can take a few years, though.

If they were established your sister has some muscles. I too would try replanting what pieces you can find.

I had one that I thought for sure was a goner, my dog ripped it out of the ground but I replanted it right away, it looked terrible all season.. but much to my surprise, this spring its back with a vengeance!