Sorry for your situation.
First of all - the tax preparer should NOT file the tax return without your signature - that is a violation from her side.
You may file a formal complain against that tax preparer with the IRS - and may request the tax preparer to compensate all damages resulted by her actions.
However - that would be a civil matter between you and the tax preparer - if she refuse to compensate or you do not agree on the damage valuation - you may only sue the tax preparer.
Your tax return is NOT shared with any other government
The IRS only deals with you and your appointed representative.
If you are required to provide the tax return to the third party - the most common way - to order your tax account transcript - that basically shows all information from your tax return.
Be sure to order transcript AFTER your amended tax return is processed.
When you file an amended tax return - there is no need for separate letter.
On the amended tax form 1040X
see Part III - "Explanation of changes. In the space provided below, tell us
why you are filing