Pre Karate Kid
When Johnny Lawrence and his friends are watching a movie, his friend Dutch bothers a few girls in front of them, throwing Milk Duds at them, Ali being one of the girls. Ali, sick of Dutch's treatment, stands up and angrily dumps popcorn down his shirt and getting butter all over him. Johnny instantly falls for her. After flirting with her a few times Ali agrees to go out with Johhny, and they kiss on their first date on a Ferris wheel at Golf N' Stuff. The two date for two years, but their relationship ends the summer before the events of the original Karate Kid. Johnny tells his top student Miguel that they got into a fight the summer before his senior year and broke up as a result, and tells his Cobra Kai friends that she dumped him when he forgot her birthday because he was too drunk from hanging out with them. This was what caused Ali to think that whatever good qualities Johnny had didn't outweigh his bad and that he was simply a lost cause.
She seems to take an instant liking to Daniel LaRusso much to her ex-boyfriend Johnny Lawrence's dismay. Johnny tries to fix their relationship, but Ali tells him to leave her alone which angers him. When Daniel tries out for soccer, she shows him what she knows before practicing with the cheerleading squad, though watching with concern after Daniel is expelled from tryouts. She and Daniel eventually begin dating. She cheers for Daniel in the All Valley tournament, and is excited when Daniel wins.
According to Daniel, Ali wrecked his car and left him for a football player at UCLA right after the senior prom.
Losing Ali forever greatly affected Johnny, as he viewed her as the one genuinely good thing in his life (aside from his mother). It also was one of the reasons why any relationships he had with other women never worked out.
She appears in a few flashbacks. She is seen when Johnny is drunk driving and reminiscing about her and his Cobra Kai friends - he smiles when he thinks about her, showing he thinks of her fondly even 30 years after their breakup. Later, Johnny tells Miguel about his first meeting and relationship with Ali (and how Daniel "stole" her from him) in order to warn him that the LaRusso family is dangerous. Daniel tells Johnny she is married and living in Denver working as a pediatric surgeon, according to her Facebook profile.
When Daniel's daughter Sam is upset over her breakup with Miguel, Daniel tries to make her feel better by talking to her about some of the girls dated with Ali being one of them. Daniel says that he was truly in love with Ali. When Sam asks why that relationship ended, Daniel refuses to disclose why, instead quickly changing the subject to his relationship with Kumiko.
At a bar, Johhny's former Cobra Kai friends talk about the time Dutch broke the dartboard and Johnny says that he got so drunk that night he missed Ali's birthday which resulted in her dumping him. Tommy, being supportive, tells Johnny that is "her loss.", which Johnny doesn't exactly agree with considering Ali became a doctor and that she married another doctor, while his own life had gone downhill. He kept the feeling to himself, considering Tommy's condition. When Johnny and his former Cobra Kai friend Tommy are talking in the woods the night before the latter's passing, Tommy tells him that he had a crush on Ali in his younger days and joined Cobra Kai in order to develop the courage to ask her out. However, he never did so as Ali was Johnny's girl, and he refused to let a woman come between him and a fellow Cobra. Johnny laughs it off, saying he has had a lot of women in his life, but Ali was "the one that got away".
After getting turned off by various women he met via an online dating app, Johnny gets on Facebook and searches for Ali. When he finds her, he contemplates a direct message for her about catching up. Despite ultimately not wanting to send the message because he did not want to look desperate, a woman at the bar accidentally bumps into him which causes him to accidentally hit the send button.
After Miguel's accident & John Kreese taking back Cobra Kai, a distraught Johnny throws away his smartphone at the beach, not noticing that Ali Mills sent him a friend request on Facebook.
According to the director, Ali will appear in this season.
In The Karate Kid, Ali has blonde curly hair, bangs, and brown eyes.
Ali cares a lot for Daniel, and is very supportive of him at the tournament. However, she obviously didn't care too much for their relationship, as she left him for a UCLA football player after wrecking his car (according to Daniel).
However, she will get touchy and defensive, if she or someone she cares about is antagonized. For instance, she got angry and vocal towards Johnny when the latter beat up Daniel at the beach, as well as when Johnny forced a kiss on her at the country club without her consent.
"Don't you EVER do that to me again!"
--Ali scolding Johnny, after the latter forces a kiss on her (without her consent) at the country club (upon seeing Daniel).