She meets him in a bar in Boulder, CO, in the year 1975, and Henry is drunk. He introduces himself, "and the air smells like Coors". They hit it off, and pretty soon afterwards, they are engaged, get married, and get a dog. The player can choose between two breeds - A beagle or a German Shepherd. Soon after the wedding, she gets a job request at Yale University in Connecticut, and either takes it or not, depending on the player's action. She becomes increasingly unable to think straight, and it is revealed that she has early onset dementia, or Alzheimer's. She is taken to either a nursing home or back home with Henry to be taken care of, and soon her family comes to the United States from Australia, and seeing her like this, takes her home to Australia with them. Henry does not argue. Her condition gets worse. Whether at the pair's home or with her family in Australia, the exact condition she's in at the start of the game is unknown. All ingame clues point to the idea that she is still alive.
From the photograph, it appears that Julia is a little taller than the average woman with dark (probably brown) wavy hair, and she appears to be in pretty good shape.
Julia is referenced by Henry many times within the dialogue of Firewatch, usually when Delilah asks him questions about her.
In a nighttime daze, Henry calls Delilah thinking it's Julia. Delilah picks up, only to hear Henry muttering in his sleep.