why do you think mary warren is so afraid to tell the truth?

1) she likes the feeling of being important, an official of the court, being a grown person.

2) she is terrified of Abigail.

Mary is afraid of Abigail; she's afraid that Abigail will kill her. She speaks up for Elizabeth at the trial, but she won't tell Proctor and Elizabeth who has accused her. Th doll gave Elizabeth is a definite issue, as Abigail has cited the needle inside as having made her sick through witchcraft. The aura is one of terror for everyone. Mary is frightened of her part in it as she should be, but she doesn't know how to get out without being accused herself.