She's exhausted from the day's work.

She is exhausted from the day's work.
应该为"is",从句以可以判断出说话人从旁边看到she，对she的行为做出叙述，若为has，表示完成时，则应为She has been exhausted from the day's work.

be exhausted 精疲力竭的 (固定搭配)

应该是 she is

be exhausted 精疲力竭的

is
后面的exhausted是个形容词

is

has

has