Mary Warren...argues for telling the truth.
Early in the play Mary Warren argues that the girls should confess to what they were doing in the woods to avoid a severe punishment. Mary Warren was not, however, doing the same things in the woods that Abigail was going.
Abigail was drinking blood and speaking in tongues in addition to dancing naked in the woods. The punishment that Abigail might face would naturally be more harsh that than what Mary Warren might face.
Abigail rejects Mary Warren's advice and bullies her into agreement with a different plan - along with the rest of the girls, including Tituba. Abigail insists that the girls follow her lead and stick to the story that she makes chooses for them to tell.
Abigail...forcefully insists that the girls stick to the story that they were only dancing and that Tituba and Ruth alone conjured her dead sisters.