I'm... pretty sure it was CBS who wanted her to leave. Then they realized that they'd made a huge mistake and pulled out her contract to force her to come back after they'd basically forced her out.

With that kind of treatment I can't blame her for not wanting to renew.

Yeah, MGG occasionally worries me as well. I think he wants to direct more than to act (pity, because he is a damn good actor), and if he got a good offer I think he'd bail on CM with nary a look back. And I would miss him like whoa. :-(