Courtney isn't in the TV show
Mona found Courtney's diary after she died. That's how she knew all the secrets.
she found Ali's (Courtney's) diary
She stole Ali's (Courtney's) diary.
Yes. She was the one that was friends with the girls so she wrote down what they told her
She didn't . She killed her twin sister Courtney who was in a mental hospital . One day Courtney switched with Ali and Ali was in the mental hospital . The pretty little liars didn't know Ali had a twin . So Courtney was acting like Ali the whole time . Courtney figured out all the pretty little liar secrets . And wrote them in her diary . Ali was jealous and escaped from the hospital and killed Courtney . Ali has been hiding in Jason's house the whole time .
Just like Mona, Alison gets a hold of Courtney's old diary and taunts the girls
you could get a pretty little liars book it might tell you what it says in alison diary.
That because courtney took alison's place and ruined her life while she was in a mental hospital. So she killed courtney who looked just like her sister alison and found out that her sister put the four friends secrets into a diary for her also to become the real A.
They're not. Only reason Mona pretended to be A and knew the girls' secret is because she took Alison's diary from outside the house when Maya left some boxes of her things there when she moved into the house in the first episode (when Courtney wad pretending to be Alison)
its called being Ali and knowing how to get away with things by being a player , etc.....
She has Ali's old diary from when she died and knows all of their secrets!
Spencer accidentally killed Mona, Mona offers Spencer the chance to be "A" with her but Spencer refuses and Mona tries to kill Spencer and they struggle but Mona ends up falling off the cliff.