An internal auditor is usually held to some standard of confidentiality. Audit results becoming public should not happen at the decision of just the auditor (except of course if there were a legal obligation to report). In that respect she proved untrustworthy for the company by her ultimatum. She basically proved that she would be willing to make Google look bad in the future. She also went public, making Google look bad in the present. Basically the same reason for letting her go as with Damore.