The problem is that this doesn't seem to be a government lawyer acting in her official capacity to form government policy. It seems more akin to a corporate tax lawyer "finding" that a specific tax-avoidance strategy is legal (or not): it's little more than a legal opinion. Actually, it's not even that, because she appears to make multiple statements about what the law should be, and not what the law actually is (an example of this would be her conclusion that RIPA's ca. 2000 treatment of metadata should be ignored given the role metadata plays in today's society). In this sense the document is more of a policy brief than a pure legal opinion, and while it may be useful to legislators, in no way does it form official government policy; it's simply an opinion that the legislators are free to use (or not) as they move forward.
I have no clue on the substantive merits of her actual legal analysis, and I would probably reserve judgment on it until legal commentators have weighed in. The Guardian piece offers no commentary whatsoever, and in this context we might want to remember that according to John Woo (who was actually shaping official policy in the US) and his thoroughly discredited "findings," torture only begins when organs start to fail.