Please factor ONE FACT into your own equation that I have never heard discussed. She would serve at the pleasure of the President. When she signs on to the job she will sign not only to do the job but she, and all other appointees, will sign an undated resignation letter. That letter will go into a safe in the White House.
So, Clinton leaves a secure job in the Senate, one she can no doubt have for life if she wants it. She goes to a job in the Administration and serves solely at the pleasure of the President. If she messes that up she is in big trouble, not just from the Administration but from people whose approval she not only wants but needs.
If he were to fire her, just where would that leave her? If he were only to THREATEN to fire her she would be in real trouble. He would have reams of evidence, recorded from day one of her service by people close to him in the White House, of the problems she has created to cause him to "have no choice" but to "encourage" her to resign.
If someone thinks that doesn't happen or couldn't happen then he or she has no serious understanding of political history. The President would take some heat, of course, but every President has survived removing people who do not play by team rules, and he makes the rules.
If Truman could survive and become more popular after firing the enormously powerful Gen. Douglas MacArthur, Obama can get rid of Clinton if she undercuts him.
More importantly, the fact that he CAN do it, and can tell her if she screws up that he WILL do it, should be enough to keep the Clintons in line.
Once she walks into the Obama tent and the flap closes her only real political hope is to do a bang up job implementing Obama's foreign policy.
Monte