Fanning's Tessa refuses to let her illness hold her back, putting together a list on her bedroom wall of things she wants to accomplish in her remaining days.
Digital Spy sat down with Fanning to discuss her "tear-duct time bomb" of a film and why she's such a big fan of her latest on-screen dad, Paddy Considine.
"There's so much going on in her body and in her mind, all the relationships she's dealing with and her own fears.
"To be able to portray all of that at once is definitely a challenge for an actor."
Now Is Good is showing in UK cinemas now.
