That's a tough one. I run into this with my in laws and I have a tendency to bring my own food when we visit. Even when I'm not trying to lose weight my blood sugar is too sensitive to eat pancakes, frosted flakes and wonder bread. Even their mayo is filled with sugar. (Miracle Whip). I'm always very self-conscious about it, especially since my MIL is a wonderful cook who loves to treat her family with cookies and other desserts. They're all very supportive, but still, I know what you're talking about. It's hard to say no to someone who went out of their way to make something they thought you'd like.

I tell my in-laws that I can't have grains per the doctor's orders or too much sugar b/c of my blood sugar. I tell friends the same thing, or just that I'm on Atkins. Sometimes that results in a dumb comment about eating all bacon and eggs, but I just shrug and change the subject.

What's going to really get dicey is explaining to everyone, including my son, why he can't have endless cans of soda or 10% juice drinks, bowl after bowl of chips, cookies, bread etc when he sees his cousins eating that way. I can't use the health excuse b/c, unlike me, he's never had more than a short cold in 17months. My husband says I'll have to suck it up and let him eat the junk when we visit. But the idea of letting my healthy little guy eat that trash makes me queasy. The worst thing he's ever eaten is all natural hot dogs and a few sips of milk shake. I think I'll end up being the crazy health food snob and pick a few of the least offensive junk items to let him eat and refuse the rest. No HFCS for my kid. Not as long as I can help it.

Anyway, if it means a lot to you, and I'm guessing it does b/c you bothered to post about it, then stick to your plan. If you explain politely that you don't/can't/choose not to eat foods with flour, that's reasonable and she should understand. At the end of the day I always think being yourself is important. And if she finds out from someone else that you wouldn't normally have eaten the brownie, she'll feel bad anyway.

Just my 2 cents