In the beginning of the movie, Lena seems to be enjoying the high life with Koopa. However, when he finds Princess Daisy, she becomes exceedingly jealous and feels that everything that she's worked for - to be by Koopa's side and rule the world with him - is in danger of being dashed to pieces. After she finds the piece of meteorite needed to merge the two worlds, she comes back to him, but he spurns her. Lena then decides to take matters into her own hands, and attempts to "help" Daisy achieve her wish of escaping by killing her. However, her attempted assassination is thwarted by the royal pet, Yoshi, attacking Lena in defense of Daisy. He grabs Lena with his tongue and pulls her towards him as Daisy runs away, but before he can actually harm her, Lena stabs him with her knife and escapes.
When Koopa learns that Lena falsely told the troops that he had authorized the invasion of the human world to begin, he realizes that she has betrayed him and still has the meteor piece. Koopa has his renegade assistant arrested and the meteor piece is returned to him, but during his subsequent battle with Mario, he drops it. Leaning over a railing, Lena manages to catch the rock; however, the railing gives way and she falls onto the wires below, which electrocutes her, leaving her burnt and disheveled. Launching maniacally, she rushes to the meteor and attempts to put the piece back in, despite Luigi and Daisy warning her not to. While completing the meteor does start the merger of the two worlds as she had hoped, it also causes a power surge that skeletonizes Lena instantly to her death and embeds her in the cavern wall behind her, thus putting an end to her aspirations of universal domination.