IRS can reduce her listed charitable contributions and assess her for additional tax liability. The omitted income item is more likely to have been separately reported to the IRS by the payor. Interest on an underpaid tax liability starts running from the due date of the payment, which in this case, was the due date of the return. There is no exemption for good-faith effort to comply. Interest recognizes the time value of money, not the good faith effort of the taxpayer.
All years are open in fraud action.
Tax return preparer penalty applies only to paid preparers.