The "Twilight" star, 22, is said to have made a move on the teenager at her co-star Taylor Lautner's birthday bash, reports thesun.co.uk,
"She was creeping on Patrick big time. People were saying they should get a room because the energy between them was so hot," a source told US magazine Star.
Stewart is currently reportedly single after her four-year romance with Robert Pattinson was called off for the second time in January.
Pattinson ended his relationship with Stewart just months after she cheated on him with film director Rupert Saunders.
He told her they would make better friends.