Two problems with this analogy. One, she left by far her most dangerous opponent alive; and two, she has effectively isolated her House.
The Lannisters are not strong enough by themselves to rule the Seven Kingdoms thru force. If it hadn't been for the Tyrells providing food and troops the Lannisters would have been crushed by Stannis at the Blackwater long ago. As it now stands, the Tyrells, Martells, and the resurgent House Stark will all be committed to the Lannisters ruin...and that doesn't take into account Dany's enormous force or Littlefinger and the armies of the Vale. She has also made an enemy of the Church, which will now fully support the efforts of the other Great Houses to bring the Lannisters down.