"Couldn't have picked a more beautiful & perfect song to start the year with," she Tweeted.
It's unclear if this song is one that will be used in the final episode for Cory's character Finn, but others in the studio Monday also praised her emotional performance.
"@msleamichele you were absolutely magnificent today," Glee's vocal producer Alex Anders Tweeted to her. "I am in awe of your strength and sweet spirit. Love you #leastrong."
Cory died of an overdose of heroin and alcohol on July 13 and his character will be written out in a special episode of the Fox series that will "deal directly with the incidents involved in Cory's passing."
Lea was also spotted wearing her "Cory" necklace yesterday.