Who is Reese Witherspoon's A-List Enemy?

Reese recently revealed that she had an A-List enemy, someone she was friends with but roasted at an awards ceremony and is now bitter enemies. Reese said "So this friend of mine - who I didn't really know that well, but she was a very serious, proper actress - she asked me to give her an award" She went on to say "I had never been to this award ceremony, so I thought it was like a roast. So I got up and I roasted her." She declared "I think she doesn't like me anymore. I thought it was so funny and it was just, I had the wrong audience." and "It was pretty bad. Yeah. Not even kidding, she doesn't talk to me anymore. Oh well" Who is it? Any ideas? Internet, do your thing and let us know.