She seems to be saying that the Wall is based on a law that permits US-based surveillance against foreign pargets if the primary purpose is foreign intelligence and not criminal prosecution. In other words, for the prevention of future terrorist attacks. Amazingly, she writes that her memo directed agents to share information, not to restrict its use! She also says (I didn't include this portion in the excerpt) that her memo was superceded by Janet Reno's memo in July 1995 that put even tighter controls on uses of intelligence (she doesn't say whether she worked on that memorandum as well).
Finally, as much as I can understand her point, she seems to be admitting that the Patriot Act extended the usage of this intelligence in obtaining foreign intelligence.
This dispute about the meaning of the Wall, and its ramifications, forcefully points out why she should be testifying in front of the Commission about the government's efforts to fight terror (where she can give a spirited defense of what she meant by the memo), instead of sitting on the commission asking questions of the witnesses.
In addition, the Wall is only part of the problem. She is a litigation partner in Wilmer, Cutler & Pickering, and I have read secondary reports that allege that her firm's litigation department is representing a Saudi leader who is defending himself against a lawsuit filed by 9/11 families. If this is so, then in my opinion this conflict alone ethically should force her off of the Commission.