It's possible that Kate Brewster, the future wife of John Connor, cameos in Terminator 2: Judgment Day. The time-traveling cyborg saga continues with Terminator: Dark Fate; directed by Tim Miller and produced by James Cameron, the sixth Terminator movie ignores the last few entries and is a direct sequel to T2. Dark Fate reunites Arnold Schwarzenegger as the Terminator and Linda Hamilton as Sarah Connor and it also features Edward Furlong making an appearance as John Connor.
As for Kate Brewster, the woman who married John (Nick Stahl) in a future timeline and helps him lead the war against Skynet was introduced in Terminator 3: Rise of the Machines. Played by Claire Danes, Kate existed in the Terminator 3/Terminator: Salvation timelines, though in the latter film, she was played by Bryce Dallas Howard while Christian Bale portrayed John. In either case, Katherine "Kate" Brewster was a veterinarian who encountered John in T3 and was pulled into the conflict against the T-X (Kristanna Loken), who had traveled back in time to kill Connor. However, the future version of Kate sent back a T-850 Terminator (Arnold Schwarzenegger) to protect John; ironically, this same T-850 killed John in the future but Kate reprogrammed it to defend him in the past. John and Kate ended T3 by taking refuge in the Crystal Peak Command and Control Center as Judgment Day took place in 2004. In Terminator: Salvation's future timeline, Kate Connor is a medic with the human Resistance and she saves John's life by giving him a heart transplant, using the heart from the hybrid Terminator Marcus Wright (Sam Worthington). Kate was also pregnant with John's child.
But let's examine whether Kate Brewster could have been in Terminator 2 all along. T2 is set in 1997 and it begins with a heroic T-800 and a villainous T-1000 (Robert Patrick) both combing Los Angeles looking for 12-year-old John. The liquid metal, shapeshifting T-1000 tactically took the form of an LAPD officer and visited John's foster home only to learn that the delinquent youth was out for the day. The T-1000 resumes his search and begins asking local kids whether they know John; the killer machine meets two young girls on the street who tell him that they saw Connor going to the Sherman Oaks Galleria. Could either of those two girls be Kate Brewster?
The two girls are played by Nikki Cox and Lisa Brinegar; they're each just credited as "Girl" in Terminator 2's cast. Further, the Kate Brewster character was created for Terminator 3, over a decade after James Cameron wrote and directed T2. In all likelihood, those two girls the T-1000 encounters were intended by Cameron to just be classmates of John Connor. Their purpose in that quick scene is to get the villain from Point A to Point B and John's reputation as a juvenile delinquent led the girls to easily point someone they thought was a police officer in his direction.
Still, it's possible to retcon one of those two girls as Kate Brewster. After all, in T3, Kate remembered John from a high school party, so they went to school together before John chose to live off the grid. Kate also has auburn/red hair and the hair color of both girls in T2 are a match. If it somehow turns out Kate Brewster was indeed in T2 all along, one of those girls would be the most likely possibility to be her.
Terminator: Dark Fate wipes away the deviating timelines of T3, Salvation, and Terminator: Genisys but Terminator 2 holds as canon, so if Kate Brewster exists in Dark Fate's timeline, she would already be alive in T2. And it's quite possible, but only an unconfirmed theory, that one of the two girls who unwittingly sent the T-1000 to John Connor's location is Kate Brewster. Now, whether John Connor is meant to marry Kate Brewster in the new timeline created by Terminator: Dark Fate is another story entirely.
