She was so exhausted that she was a shadow of her former self.
She was so worn out that she was a miserable sight.
すごく疲れている時にこういう表現も使えます：
drained
wasted
tuckered out
haggard
pooped
tuckered out
dead on (her) feet
spent
ところで、ハイフンなしで「worn out」です。「worn-out」は形容詞です。例えば：
After the marathon, I saw a lot of worn-out people.
マラソンの後、果ててる人を何人か見ました。
アメリカ合衆国 
