Be a post whore!

[Clodfobble]

The worst best way to fix a lie is with another lie, I've always said. Look at the ingredients list on the brownie box mix, and estimate rough amounts in descending quantity order, using other recipes as a guide. Give the list to her, and when she asks where in the world she can get Sodium Diphosphate or whatever, just shrug and say an American friend sent it to you, you've never been able to find it there in Aylesbury. Tell her it's the most important ingredient, and to look online for it. She'll never bother.