On my essay, I accidentally made a typo
I typed Federal Reseve Economic Forecast Forum as Federal Reserved Economic Forecast Forcum…
Do I need to tell admission officer about this? I am going to send her email anyway, but I wondering do I need to bring it up?
No - don’t bring it up.
It’s just one letter, so don’t bring any attention to it. You’ll be fine; most likely, they’ll know what you mean. Also, it’s not like they’ll deny you because of a tiny spelling error.
So I guess I am too overreacting ?
Yes, don’t worry, you’ll be fine 
I know that you say you’ll be contacting the admissions office anyways, but there’s no reason to draw attention to this tiny mistake that the adcoms themselves may miss. And this definitely won’t be a factor in their decision to admit you or not.