manage former manager

Yes, she might. But worry is like a rocking chair - it gives you something to do but it doesn't get you anywhere. Anybody coming into a department could upset the apple cart... in fact, it's the ones you least expect to do it that create the most havoc.

Meet with her in advance as you would any internal transfer, and welcome her back. Focus on all that she brings to the table. If SHE asks YOU whether YOU're worried about having someone as GRAND as HER working for you, just politely say no, with all the bored confidence you can muster.

Be clear that you expect great things, and that you expect her to understand that there probably will be a fine line she has to walk when others potentially behave around her in a way to suggest they're confused about whose department it is. You'll be expecting her to set the example of what her role is and how to be effective in it. And, if she blows everybody away, you'll be the FIRST to encourage her to have more and more responsibilities, and you wouldn't mind at ALL working for her someday.

If there are issues, give her feedback, plain and simple. Let the first few small things go if you can, to avoid being perceived as having a hair trigger on this issue.

And, visit with your boss to make sure that you and he/she are on the same page about the former manager's role and yours.

You'll be fine. There's a lot more role power at your disposal - lightly wielded - than you realize.

Mark