Kaylie Cruz is the daughter of Alex and Ronnie Cruz and the National Champion from The Rocky Mountain Gymnastics Training Center ("The Rock").
During Nationals, Kaylie beat out Kelly Parker to become National Champion. She later develops anorexia and during the tryouts for the Worlds' team, she faints during her beam routine which sends her to the hospital. Kaylie makes the team on the condition that she is deemed medically fit to compete.
Kaylie ends up in rehab for her anorexia where she befriends a model named Maeve who teaches her how to "play along" in order to get out of rehab. Despite all of her attempts, her parents refuse to let Kaylee go back to gymnastics training & Kaylie refuses to admit she has an eating disorder, but after Maeve dies of heart failure due to anorexia, she finally admits that she needs help.
After Kaylie is medically cleared, she goes back to training and ends up revealing to the public about her eating disorder.
The team ends up winning Gold at Worlds and Kaylie begins dating Austin Tucker, but in season three, Austin gets cut from the men's Olympic team & blames it on a move that Kaylie suggested & blames Kaylie for not doing well which ends their relationship, but after Kaylie's drug test turns up positive & she ends up being eliminated from the women's Olympic team, Austin comforts her & they start to reconcile.
In the end, it's revealed that Wendy Capshaw is kicked off the women's Olympic team for drugging Kaylie which gives Kaylie a spot on the team.
Kaylie broke the rule stating that no gymnast is allowed to have a boyfriend by dating fellow gymnast Carter Anderson. Her friend Lauren Tanner slept with Carter at a kegger in the episode "Blowing Off Steam." The truth comes out in the episode "Where's Kaylie?"
Kaylie then was mad at both Carter and Lauren. When Summer Van Horne tells Sasha that Carter was dating one of the Rock girls, Sasha expels him from the gym. Carter, even when Sasha asks him, does not say who the girl was whom he had a relationship with.
After Kaylie's win at Nationals, she and the Men's Silver Medalist, Nicky Russo were placed together for advertising purposes. At first, they did not get along because Nicky thought she was a brat who came out of nowhere to get the gold medal and Kaylie thought Nicky was arrogant and mean. However, the two put aside their differences.
After this, Nicky transferred out of the Rocky Mountain Gymnastics Club (otherwise known as The Rock) to the Denver Elite Gymnasts Club (where Kelly Parker trains) because he wanted to get away from the drama at The Rock.
Kaylie decides to swear off boys and focus solely on gymnastics, however in Season 2, she meets Austin Tucker, a gymnast who won a Gold medal at the 2008 Olympics. Austin cares about Kaylie and notices she is not eating. Austin's little sister went through an eating disorder so he tries to help Kaylie.
When Kaylie collapses at the Worlds' tryout, Austin catches her before she falls off the beam and is seen holding her hand at the hospital. Austin has also punched Damon, Emily's boyfriend.She falls in love with Austin Tucker and they end up dating. While dating, Kaylie tries to help Austin with his floor routine to survive the last cuts to get onto the World's Team that is headed for the Olympics.
To show her support, she gives him a page from her diaries as good luck. While helping out, Kaylie shows her opinion for his floor routine and Austin takes her advice by changing it to something easier for him.
After going his turn, Austin meets with Kaylie believing that he made the finals cuts claiming that they didn't even want to see his rings routine. Austin then finds out he doesn't make the team and blames Kaylie for distracting him and ruining his dreams of going to the Olympics for another gold.
Kaylie goes to his room to see if he's still there, but sees that he is already gone and on his bed is a box that is supposed to be sent to Kaylie. Inside of the box is the frame with her diary entry. This marks the end of their relationship.
After she was told she got disqualified from the pills Wendy put, Kaylie was packing her bag, but then Austin apologized because he overreacted and felt ashamed. Before the end of the series, Kaylie and Austin reconcile.