You are better off ignoring it.

If you are in business, and you pay a contractor more than $600, you are required to issue a 1099-MISC, even if the person does not have a tax ID number.  If the person does not have a tax ID number, you are required to withhold 30% of the payment as mandatory backup withholding and send it to the IRS.  If the person files their tax return, they get credit for the withholding.

Going back to fix this problem would call the IRS attention to the fact that you did not make the mandatory withholding, and could subject you to penalties.

I assume you already deducted the expense as a business expense, so there's nothing to amend for your tax return, it would just be issuing an out of date 1099, which could also in turn lead to your contractor getting a letter, asking if she already reported the income or if this was new income.