Testifying against a friend or community member is not coercion if people ascribe negative outcomes to not just their well-being, but to the well-being of their friends.

For instance, my testimony gets me out of jail, but it helps put my friend in jail: the degree my testimony impacts that sentence, and the sentence itself, have to be factors in the decision.

Thus, and without getting into Manning's thought process, I wouldn't be surprised if she believes the negative effects (real or perceived) of her testimony outweigh the stay in jail.