The Last Of Us got a remake last year. A polished version of the original game for PS5 that added new elements. Among them are nods to Part 2 which launched two years prior, including hints that Abby, who isn't introduced until the sequel, would become a big part of the series.
Pointed out by the appropriately-named AbbyStanAccount is an image you can see in the mall during the Left Behind DLC. The ad shows a blonde woman working out with the message “coming soon” written across it. Since that ad wasn't there in the original game, and Abby is a muscular woman with blonde hair, fans have surmised this was added as a retrospective homage to the character.
It might seem like a reach to some of you, but the image being added for the remake does strongly suggest it was a hat tip to Abby long before she was officially introduced to The Last Of Us timeline. AbbyStanAccount also points to some other new posters in the mall that resemble both Owen and Abby, and those aren't the only elements of the first game that were altered with reveals from the second game in mind.
Be warned, the rest of this article features some big spoilers for those of you who haven't played the games and don't want to know what happens in this Sunday's adaptation finale. The model of the surgeon who is preparing to operate on Ellie has been changed to how the then-introduced character looks in Part 2. The way his body is left is also the same way it's found when Abby discovers it, the moment her quest for vengeance against Joel truly begins.
Abby hasn't been introduced to the TV version of The Last Of Us, of course, and unless HBO hits us with a Marvel-style credits scene, we won't know what the live-action version of the character looks like until season two. Some fans have fantasy cast Florence Pugh in the role, while others believe the show's creators have already cast Shannon Berry as their Abby.