well you have to think that since she took madara's body which had what he already had plus the juubi/shinju chakra. as she was taking madara's body she absorbed the chakra of everybody in he world who was caught in the genjutsu. so it's expected that she would have enormous amounts of chakra. as for the kyuubi's statement of the juubi being immeasurable, it has more to do of naruto's level when trying to measure the juubi's chakra. if he himself had the levels he has now, it would have been different.