[1] One of her first roles was in amateur theatre performance, playing the mother of a spoiled girl wanting new jeans.

Eli initially tells Oskar to fight back, and rescues him in the end, killing three of the bullies in the process.

Because Eli is supposed to be an androgynous character in the film,[8] director Tomas Alfredson decided to overdub Leandersson's voice with a less feminine one.

[10][11] In an interview with Dagens Nyheter, Leandersson laughingly commented that "it was actually nice to be dubbed, my voice sounds weird".

"[15] When asked about the biggest challenge in making the film, Alfredson mentioned the fact that people already would have a perception of the characters and the surroundings from the novel.

[16] On another occasion, he again commented positively on Leandersson's appearance, stating that "[w]e hardly used makeup or anything in post-production to make her like this, she is simply damn good.

According to Karen Durbin of Elle, she "evokes Eli's radical apartness with an air of watchful caution and a contained stillness of body that not only belies her childish appearance (...)", and "In a performance devoid of sentimentality she perfectly captures the awful solitude of a creature who exists outside time".

[18] James Berardinelli also praised Leandersson for "crafting an individual who is both mysterious and compelling",[19] while Justin Lowe of The Hollywood Reporter wrote: "The youthful actors imbue even the most emotional and disturbing scenes with remarkable complexity.

"[21] The Oregonian called Leandersson's performance "incredible", and expressed doubt that any actress in the American remake could top it.

[22] While Swedish reviewers generally made positive comments about the two leads, Emma Engström of Göteborgs-Posten felt that Leandersson's character was lacking in depth.

[6] In an interview, she noted history was her favourite subject, because she finds it "interesting to know how people lived and died in the past".