One thing that it sounds like she did but I want to be a little more specific about is sorting messages. When you have that many, I recommend that you sort your messages first by sender. That helps you get rid of all the *s*p*a*m and non-essentials like newsletters. Then take the remainder and sort by subject line. This helps bring to the top those that might be urgent. And lastly sort by Received so you can deal with what’s left on a first come, first serve basis.
I highly recommend that you read the whole story at Simple GTD.