Delphi IXMLDocument Out of memory

Question

I'm parsing a very large (108 MB) XML with IXMLDocument and unless I compile into 64-bit I get an Out of Memory error. Checking RAM usage during parsing the app is using up to 2.5 GB of RAM, which seems quite excessive. Am I doing something wrong?

procedure TMyDoc.ReadXML;
Var z: TZipFile;
    i: Integer;
    mem: TBytes;
begin
  z := TZipFile.Create;
  z.Open(fFileName, zmRead);
  i := z.IndexOf('word/document.xml');
  if i > -1 then begin
    z.Read(i, mem);
    TBytesToString(mem, XMLData);
    XMLData := UTF8Decode(XMLData);
  end;
  z.Free;
end;

procedure TMyDoc.Open(Filename: string);
Var i: Integer;
    Data: IXMLNode;
    Node: IXMLNode;
    SubNode: IXMLNode;
    XMLDoc: IXMLDocument;
begin
  fFileName := Filename;
  ReadXML;

  XMLDoc  := LoadXMLData(XMLData);
  XMLData := '';
  Data := XMLDoc.DocumentElement; // w:document
  Node := Data.ChildNodes.FindNode('w:body');

  for I := 0 to Node.ChildNodes.Count-1 do begin
    SubNode := Node.ChildNodes[I];
    ParseChildEntities(SubNode);
  end;
end;

procedure TMyDoc.ParseChildEntities(node:IXMLNode);
Var i: Integer;
begin
  if not Node.HasChildNodes then Exit;

  for i := 0 to Node.ChildNodes.Count-1 do begin
    // some parsing/processing within the current node
  end;

  // iterate through all the childnodes
  for i := 0 to Node.ChildNodes.Count-1 do
   if node.ChildNodes[i].HasChildNodes then ParseChildEntities(node.ChildNodes[i]);
end;