In the beginning of the series, she only made appearances chatting with the other Battle Brawlers in a chat room on the site, and would usually be eager to hear if Dan had won any battles or not. Although it is not directly mentioned, it seems that while Julie now lives in Japan, she moved there from America.
She makes her first live appearance in A Perfect Match, battling her childhood friend Billy and being defeated easily due to the appearance of his talking Bakugan, Cycloid, making her upset that all her friends had talking Bakugan. On a day off from school, she spent the whole day looking for one, almost getting stung by scorpions, bitten by venomous spiders, and falling off a steep cliff, with absolutely no results. After returning to her room, in her depression, she started crying, until a Bakugan named Gorem spoke to her. Gorem befriended her, and together, they defeated Billy in a rematch.
When she discovers that Billy had joined Masquerade, she is crushed by this fact.
In Duel in the Desert, she and Shun challenged Komba, her neighbor, and Billy. In their battle, she lost bothTuskor and Rattleoid (although they reappear in episode 19), and nearly lost Gorem though with Shun's help, he was saved. By the end, they pulled it together and defeated them both.
In Julie Plays "Hard Brawl", she follows Dan around since she is still upset over Billy, which resulted in Runo calling her a "dog". She states that she would do anything to free Billy from Masquerade's grip. This leads to another brawl between the two and almost leading her and Gorem to be banished to the Doom Dimensionforever. Fortunately, she was able to convince him otherwise, and Billy ends up quitting Masquerade's team.
When Billy was defeated by Masquerade, somehow Julie sensed that something was and wrong, and it was proven true when Joe Brown told everyone about what happened to them.
She watches Dan's match against Masquerade and tries her best to encourage everyone after he was sent to the Doom Dimension with Drago.
When the brawlers ended up in the Doom Dimension with Dan, she tackled him to the ground as usual, but didn't seem happy to see them, at first.
She is then tested by Clayf, one of the Legendary Soldiers of Vestroia in Nightmare in Doomsville. In order to return to Earth, she must battle against an illusion of her sister, Daisy, making her think she wasn't special and how Daisy would always out do her at everything. Her realization that she is special and doesn't need to compare herself to her sister, allows Gorem to evolve into Hammer Gorem.
She makes another appearance during Dan's test and along with the rest of the Battle Brawlers as illusionary clowns.
She battles Dan first in Home Sweet Home to get Drago to evolve, where it is revealed that she has moved up to eighth place in rankings. At first, he didn’t want to battle her, worrying that she would fall off Hammer Gorem, but due her words of encouragement convince him to use his ability, win, and catch her before she fell.
When the Brawlers were in Vestroia, she didn't do much in the Ventus/Aquos world besides having Hammer Gorem find the next world. She and Runo stay behind in the Subterra/Haos world to slow down the Subterra-Haos Hybrids Rabeeder and Tricloid, challenging them to a race and stalling for time until Dan and Dragoreached the portal. When Drago and Hydranoid thought they defeated Centorrior and Druman, Julie and the rest of the gang re-appear, although they never revealed how they were freed.
She later faces Tricloid again alongside Billy and Nene in Here's Mud In Your Eye and defeat her. It was also revealed in that episode that Julie and Billy really did have feelings for each other and of course she asked Billy on a date to which he said "yes."
She later helps Dan and Drago to defeat and destroy Naga.