What do we know about Aiden:

Backstory: Aiden Burn was fired by Mac Taylor for tampering with evidence in the case of D.J. Pratt, a rapist she is trying to nail. She is later killed by D.J. Pratt.

Relationships:

Danny Messer: They may have had an unofficial romance after she was fired, but while she worked for Mac, they had a close friendship. They occasionally flirted, but that's about it as far as we know.

Defining Cases (or Episodes):

Secrets:

Trivia: She and Danny may have started unofficially going out after she was fired.
Her murder made Lindsay feel a bit uncomfortable seeing as how Aiden was close to everyone, especially Danny.

Quotes:

"He died because of his wife, and she was the only one who loved him."