Could You Repeat That?

My boss has this most annoying habit of re-sending mass distribution list emails we have already received to us.

As in, she hits "reply all", puts her 2 cents at the top of the email, and hits "send".

"Guys, this is very important. I know you might not have seen this before, but you should read this."

Duh, we just did. Yesterday, when YOUR boss sent it to us.

The reason for this eludes me. Is she trying to reiterate? Does she not see that we have already received the email? Is she trying to take credit for someone else's work? Is she a stark raving lunatic?

All of the above?