The Politics of Shea-Porter's Amendment

So, the thing I don't understand about Carol Shea-Porter's amendment rolling back the National Security Personnel System is this: why didn't she call the Obama administration to coordinate it? The amendment was always going to conflict with the NSPS review the administration has under way. I don't see any particular reason the amendment HAS to be attached to the appropriations cycle. I understand Shea-Porter's desire to get things under way, but the review committee's going to issue its results in August or early September. Would it have been so disastrous for her to wait a couple of months, coordinate with the White House, and have everything go smoothly?