Holly is introduced at the outset of the series as one of the best friends of Summer Roberts and Marissa Cooper. After the fashion show Holly holds a party at her house as a reward for their good work for charity. She tells Summer that she thinks Ryan Atwood is cute. At the party people are doing drugs and drinking alcohol. She is then seen with Summer carrying Marissa who has passed out due to alcohol. They can't find Marissa's keys to let her in her house. They can't wake her parents as Marissa's dad would go ballistic. So they leave Marissa passed out on Marissa's driveway.
She holds Summer's birthday party at her house. However, Marissa doesn't attend because she is in the model home with Ryan. She is later seen holding another party at her house. Summer tells her that she hopes Holly's parents never come home. She also says that she heard Ryan Atwood is a total psycho.
She is later seen at the dance practice for Cotillion. After practice, she walks over to Marissa who is talking to Seth Cohen and Ryan Atwood. She tells them that she is holding a party at her house. She does it every year for cotillion. Seth says she didn't do it last year, and she tells him that she did. This means that Seth wasn't invited. Later she is seen with her father Greg Fischer buying things for her party. They run in to Marissa's dad, Jimmy Cooper. Jimmy tells her to have a good time at the party as Marissa is going. Her dad tells her to take the bags to their car. Her dad talks to Jimmy, and tells him that he wants to invest in a company. He tells Jimmy that they need to pull $250,000 out of their investment account. Jimmy tries to talk him out of it by telling him that the market is about to turn around.
She is then seen at the party talking to Summer. Summer tries to get her to trade escorts for Cotillion, but Holly won't switch. Then she is seen at Cotillion.
Her father, Greg, then discovered that Jimmy Cooper has been stealing money from his clients, a revelation that leads him to punch Jimmy at Cotillion.
She is next seen holding another party at her house. Marissa has now broken up with her boyfriend Luke Ward. Holly approaches him at the party. She asked him where Marissa is. He tells her that she is at home and they are taking a break. Holly says "you are" and feels his chest. She asks Luke if he is okay. She is later seen making-out with Luke on her bed. Luke asked her if she knows how long he's wanted to do this. She replies "as long as I have". She then says that he and Marissa should have broken up a long time ago. They hear something smash downstairs. So they stop to see what was broken. She yells at the person saying "That's my blender". The person ends up shooting Luke.
Every year they take a trip to Tijuana before school starts. Marissa decides that she isn't going to go, and she will stay home with her dad. Holly is at the crab diner with Summer, Luke, Marissa and the rest of their gang. Marissa tells them she isn't going. Summer now can't get a lift as Holly's car is full. Holly and Luke are talking away from everybody. Holly tells Luke "what happens in Mexico stays in Mexico." Luke tells her he can't because he and Marissa are back together. She then says that she thinks it will be a week before they break up again. Then she says that he will miss her.
In Tijuana they are in a club called Boom-boom. Holly starts touching Luke. But Luke tells her he isn't interested. Holly tells him that Marissa's not even coming. She then says that she loves the song and they dance together. They then start touching each other and kissing. Ryan, Seth, Summer and Marissa then enter the club. They look around to find Luke. Then Marissa spots them dancing and kissing.
Marissa walks over and asked what they are doing and how could they do that to her. Marissa then tells Holly never to talk to her again. Summer then says to Holly "you're such a bitch". Holly then says that Luke "hooks up with everyone". Luke tells her to shut up. Holly continues. "Freshman girls, Girls from Mater Dei, Girls from UCI" (both actual schools in Orange County). Marissa asks Luke if that is true. Luke appears guilty. Holly then says, "Marissa, everyone knows. Everyone! Now you do too." Summer then says that she is so mean. Holly then says "Summer, I am honest." Summer then pushes Holly and shouts "Her parents are getting divorced". Seth then tells Holly to walk away because Summer suffers from rage blackouts. Marissa is then depressed and takes an overdose of pills as a suicide attempt. However, she is found by Ryan, Seth and Summer and she lives.
Then she is seen at school. She is at a table full of girls. Marissa walks in. Holly says to the girls, "Did you know that she overdosed on Vicodin?" They all then laugh at Marissa.
Summer and Marissa blank Holly from then on.
Holly appears once again in Season 4 in The Chrismukk-huh? episode when Ryan and Taylor Townsend fall into concurrent comas, which then situates the narrative in a putative "parallel universe." In this universe, Marissa died from the overdose in Tijuana, and Holly has continued to be very close friends with Summer. The two are highly materialistic and vapid, and use hip-hop slang. It is strongly hinted that Holly is also having some type of an affair with Summer's fiance in the alternate reality, Chester (Che's alternate persona).
In a later episode, The French Connection, it is revealed that Holly got married the previous summer (ie, shortly after she presumably graduated high school). Hoping to find out what married life is like, Summer meets up with her. Holly introduces Summer to a couple of other recently-married young Newport girls. They collectively refer to themselvs as the "Newpsie-weds" and live an incredibly shallow lifestyle of going to the gym, going to lunch and shopping. The "Newpsie-weds" try to help Summer plan her wedding to Seth, and suggest that Pancakes (Summer's pet rabbit) should be the ring-bearer. As they've decided that the wedding should be pink-themed, Holly is about to dye Pancakes pink as a test to see how she will look. Summer realises that marrying Seth is the wrong thing for her to do, and that she doesn't want to live like them and she saves Pancakes from Holly's big pot of pink dye.
Holly next appeared in the flashbacks in The Case of the Franks, which were set in 1998. In the flashbacks it showed that a younger Summer and Holly when they were 10 years old were best friends and they attended class with Seth, Taylor, Luke and Marissa (not seen). They made fun of Taylor Townsend and call her Taylor Dorksend.
In The Shake Up, Holly made her final appearance at a yoga session for pregnant women, where she met the newly-pregnant Kirsten Cohen. Introducing herself as a former classmate of Seth's, Holly tells Kirsten she has just found out she is pregnant. She confides in Kirsten that she has no intention of letting her body turn into a "dumpy baby factory" as she has worked way too hard to be in perfect shape, adding "Who says I can't have a baby and a six pack?"
Holly then calls over her two friends, who congratulate Kirsten on her pregnancy. The three pronounce Kirsten to be "ripped" and invite her to join the club they've formed. They have all promised they will never look like "Molly the Mammoth," another (normal-looking) pregnant woman in the class, and intend to keep their figures and not let pregnancy interfere with looking good. One of them says that in nine months she will still be wearing a bikini, while the other says that if she gets too big, she will induce her baby at eight months, as it is easier to lose the weight. Holly tells Kirsten the club is called the "Six Pack Pack" and asks "Isn't that like so cute, you just wanna barf?" "All the time." Kirsten replies.