What does mary warren admit in court

She initially admits that the whole witch hysteria thing was not real but quickly recants when Abigail subtly threatens her and the other girls begin to scream and holler.

Also I think that while Mary is rather spineless, she lacks the maliciousness of Abigail. Abigail's threats combined with the threat of the court of hanging, the court is not interested in the truth, cause Mary to buckle under pressure.