I have just recently been promoted and a new assistant was hired for me, in my former position.  The person who left my current position and my new asst. are very close friends, and still in contact with each other on a daily basis.  The person who left did not do so on friendly terms.  She was angry she did not get the promotion to a Regional position, did not even get an opportunity to apply for the Regional position, so she left on a very bad note.  The new Regional person is supposed to be training me in my new position, and is doing so, but it is slow going.  In the meantime, the "outsider" is feeding information to the new assistant on how to do things that I don't even know yet, in an effort to make it look like the Regional is not competent, and in so doing, it makes me look incompetent.  The other side of this problem is, that the new assistant, as I have been training her, still cannot do some of the simplest day to day requirements of her position without help, and yet at times she answers questions or performs/executes skills that I know she could not possbily have done on her own and has to be getting help, because I don't know how to do these things after having been in the assistant position for over 2 years.  I have the feeling that the "outsider" is feeding her information, but I can't just forbid her from talking to this person.  As a matter of fact, I've already discussed this with our GM, and I believe he spoke with her about the ethics of the situation.  She later said to me she was keeping their friendship outside of the office, but I myself have seen the "outsiders" phone number pop up on her caller ID and our receptionist knows that the "outsider" has called in.  Is there any way to stop this sabotage/subterfuge?