Bella, who uses gender-neutral pronouns, plays Ellie in the HBO drama, set in a post-apocalyptic future where humanity has been almost wiped out by cordyceps.
The deadly parasitic fungus turns humans into zombie-like creatures, but Ellie is immune from infection and is humanity's last hope for a cure.
In the first season viewers saw a father-daughter relationship slowly blossom between Ellie and mercenary Joel, played by Pedro Pascal.
After escorting the 14-year-old on a dangerous journey across the USA to meet doctors working on a vaccine, it becomes apparent Ellie must die for a potential remedy to be produced.
Rather than sacrifice her, Joel kills the medics and flees with the unconscious teenager.
When she awakes, he lies to her about what happened, and season one's cliffhanger ending leaves viewers with the strong impression that Ellie is well aware of the deception.