Before a camp counselor meeting begins, she plays a prank on Miranda Gardiner, head counselor for Demeter's Cabin, by literally removing her nose from her face. She eventually gives it back when Chiron asks her to, because he wants to start the meeting.
Lou Ellen, along with Nico di Angelo, Will Solace, and Cecil Markowitz, set the Romans' onagers off-course before they can fire on Camp Half-Blood. She uses her Mist-controlling magic to hide the four demigods from the Romans so they can complete the task without getting spotted, but eventually, the magic wears off and they are seen. She argues against Octavians' accusations against the Greeks; saying "And the men who were about to burn our camp to ashes?" suggesting a large amount of loyalty to the Campers and a protective nature. In the process, she uses a Pig Ball, a magical item property of Hecate cabin, and turns six of the Roman guards into piglets. This is remarked on by Nico in high praise, causing her to blush. After Gaea's defeat and the end of the war, Lou Ellen turned the Romans back to normal on Chiron's insistence, albeit somewhat reluctantly.
Lou Ellen was mentioned to have done Cabin inspection along with Travis and Connor Stoll. During Cabin inspection, she made other people's personal items disappear by manipulating the Mist which later reappeared.
Lou Ellen's appearance is never described in detail though she, along with the other children of Hecate, may have inherited her mother's dark hair and green eyes.
- Mystiokinesis: As a daughter of Hecate, she can cast and manipulate magic.
- Mist Control: As a daughter of Hecate, she can control the Mist. This ability means she can alter mortals' memories and perceptions, also she can use it to summon a 'Mistform'.
- She can create illusions.
- She can create false memories.
- She can make monsters invisible or have them be seen as something else.
- She can hide locations.
- She can summon Mistforms.
- She can disguise and hide people.
- She can disguise and hide objects.
- She can influence the minds of mortals.
- She can teleport through the Mist.
- Pig Ball: When defending the camp from the legion, Lou Ellen uses a pig ball to turn legionnaires into piglets. When she changes the piglets back, she does so grudgingly.
- The second part of her name, 'Ellen', means 'Torch'. This could be a reference to her mother Hecate, as her attributes are twin torches.
- The first part of her name, Lou, is a Greek name, however, Ellen is not.
- Due to the translator's mistake, in the Polish version of The Lost Hero, Lou Ellen was introduced as a boy.