Bonnie is the daughter of Drew MacFarlane, the owner of MacFarlane's Ranch and has spent her whole life working on the ranch with her father. When she was young, her father hired a "French" governess (who Bonnie suspected of not truly being French, due to the fact she spoke Russian) to teach her and keep her civilized. She had six brothers, but five of them died from either illness or foolish choices. Her sole surviving brother, Patrick MacFarlane, moved to New York, where he supposedly works as a banker in Manhattan. With the majority of her generation deceased and the only other surviving male child leaving the family, Bonnie feels it is up to her to become the "man" of their family's ranch.
It is unknown if she ever learns of Marston's death.
By 1914, Bonnie has already gotten married, though it is not stated to whom. Jack Marston is still welcome at the MacFarlane's Ranch and is able to make use of the cabin his father once recovered in. Bonnie is not seen by Jack, although the ranch operates just as it did in 1911.
In 1914, NPCs can be heard discussing that she found a husband.
Bonnie appears at the ranch, seemingly unfazed by the zombie epidemic, but seems mentally disturbed from her words. She nonchalantly tells John that her father Drew MacFarlane was rounding up the undead in the barn and was there since the day before, and asks John to check on him, which begins the side-mission "Paternal Pride". After John tells her the fate of her father, she states she is glad that he fought protecting those he loved and walks back into the house. After that, she isn't seen for the rest of the game.
Bonnie shares a few similarities to Annie Stoakes from the previous game Red Dead Revolverboth are ranchers with blonde hair and similar outfits and they both face similar threats during the games.
Bonnie's age is discussed in the first issue of the Blackwater Ledger after the mission to free Bonnie from the hanging noose. The article, found in the lower left hand corner, suggests her kidnapping was a crime of passion perpetuated by the Bill Williamson gang and goes on to describe Bonnie as "a spinster of 29 years." This contradicts Bonnie's own statement in "This is Armadillo, USA" that she is 27, as well as the guide which lists the same age; this may be an oversight on Rockstar's part, though it's also plausibly an in-story misreporting.
Bonnie MacFarlane is named after the aunt of former Rockstar San Diego designer Rob Hanson. He renamed the ranch he designed "MacFarlane's Ranch" and named the rancher's daughter Bonnie MacFarlane just before he resigned.
Bonnie appears on the back of the fold out map provided with the game.
Her outfit used to be able to be bought and worn within PlayStation Home.
In the Undead Nightmare DLC, a graffito will appear on a wall in Blackwater reads "You do so love to talk in riddles". This quotes Bonnie's statement to John. Another quote from Bonnie found scrawled on the walls of Blackwater is "Civilization is truly a beautiful thing."
She was #29 on Game Informer's The 30 Characters Who Defined a Decade.
On close examination, it can be seen that she wears two belts like most male characters, a regular belt and a gunbelt.
John only calls her "Bonnie" twice in the game; the rest of the time he refers to her as "Miss MacFarlane."
She can be seen wielding a Winchester Repeater in artwork but in the actual game, she never had one.
Bonnie appears to wear a Native American themed necklace.