For sure June. I make from scratch too. I've tried a couple of box cakes and some of them are OK (Mick is working his way through one at the moment), but there is just a certain something there that I can't put my finger on, but that lets me know it isn't one of mine.
I hear ya.
You aren't being anything to her. Sounds like she is asking for quite a lot from you and should expect to pay extra for the extra you are doing to make her happy,. Just explain it to her and right away. If she doesn't like the price then send her on her way. See if she can gegt anyone else to do what she wants for the price you're doing it for.
If the client is changing things on you and creating more work you are certainly entitled to be complensate for the extra work. We all know that it isn't baking and the ingredients that cost so much but are time and attention to the work. It is not unrealistic and telling her so is not inappropriate. It is business and nothjing more.