Suggestion?
In the future addess the income front and center with an explanation why you did the income the way you did, and as a side note, explain to her averaging salary would not be appropriate, nor would penalizing her for a business that is now defunct. (can you prove that? Disconnected telephone number, account or service no longer subscribed too, etc).
You may have done a memo to file - and if so, you have an underwriter flexing the muscles. The object in the submission is not to make the Underwriter think. Make their lives easy and they will reach for your files every time. It sounds like she's shooting from the hip and now you are challenging her knowledge and ability. Go with an easy hand, but before you do, be sure you can address:
Any write offs on the 1040's for the primary job?
Your VOE has the breakdown for salary v. commission?
If she has zero write offs on primary job, you have an excellent chance of using the YTD in the average (w/ prior years COMMISSION). If not, can't use unless you have a compelling reason. (change in company policy, company will now provide car in lieu of her write offs, etc)
Can you document the other business is indeed gone? Accountant letter? Notification to local taxing authorities? You will need something. Distributor letter? If you can't prove a little loss of 26K is not going to happen again, that must be included. (No one loses 26K on Avon.....you need to give more details on this side job).
There is nothing about this that screams impossible.....but if these things were not in the file, I think I understand where she is coming from. Flat averaging the income is standard when there is insufficient documentation and without the documentation, there was zero incentive to make the deal work. (you didn't give her anything to work with......telling her the business is gone, won't cut it). She threw it back at you to fix. She would have killed it if there wasn't a chance.