Try some different slugs and shoot it off a bench, rest, or shooting sticks etc to make sure its the gun (no offense). I stongly suggest trying to find a slug it likes, I suggest Brenneke MP's (!!!), Federals or Winchesters in the 20 gauge.
Another thing to do after you find the slugs it likes is have the barrel drilled and tapped for a H&R scope rail (I suggest the Ultra rail) and put a low power shotgun scope (with plenty of eye relief) or a red dot on it.
You do have a great deer gun there for your daughter if you put a bit of time into seeing what it likes to shoot (not MAGNUMS please!!!, your daughter will thank you and the deer will never know the difference) and perhaps inhance the sighting arrangement a bit, but that is not neccessary if your daughter is up to the task of shooting accurately....<><.... :grin: