Fandom: Danny Phantom

The daughter of a scientist at Axiom labs is fatally wounded in an accident and her dad uses his research into ghosts to save her, but the process gives her ghost powers. She's half ghost. But, unlike Danny, she needs her ghost powers to keep her alive. Without them, her vitals fail. If she overexerts herself, it can drain her powers to maintain her life.

The president of Axiom Labs sees the potential of having a ghostly agent. He uses her to trap ghosts so they can study them.

When the Fenton's ghost portal starts spitting out ghosts left and right, she's sent to Amity Park to find out what's going on.

She meets Danny Phantom while capturing the rogue ghosts that escaped through the Fenton's Ghost Portal. She returns to Axiom HQ and reports to the lab President, asking if she can go undercover and learn more about this ghost boy. He agrees on the condition that she check in every week.

She befriends Danny Fenton and quickly realizes that he and his friends - Sam and Tucker - are keeping something from her. She eventually discovers that Danny is the Ghost Boy, but doesn't tell him, not sure how to.

During an attack by Skulker, she saves Danny and gets caught. Skulker takes her to Plasmius, who learns that she's half-ghost. He tries to get information out of her and convince her to help him.

Danny and the others rescue her and she explains who she is and how she got her powers, but she doesn't tell them everything, afraid of what telling them about her mission would do to their friendship. They learn that she knows Danny's secret and they let her join their ghost-hunting team in both forms.

That's about it. I waited too long to finish so now you get a vague description. 😅