This was discussed at some length here:
http://www.skepticalviewer.com/2008/01/29/ps-school-house/
As for why she doesn't conduct her own investigation, good question. The only answer I can think of is that she probably has, but since these sorts of investigations always turn up no evidence or ambiguous evidence people always want to go back and hope their team will find something new. Although, just thinking about that is rather suggestive of the notion that all of this ghost hunting is rather silly and pointless. C'est la vie.