I wouldn't risk eating food at someone else's house. Even if the ingredients in the dessert are gluten-free, the risk of cross contamination is high. Especially if she's making a gluten-free baked good. Or cutting fruit up on her bread cutting board. Or "Oh, that spoon isn't that dirty. I'll reuse it mixing up this other dish." Each exposure to gluten can potentially lead to more health problems down the line. Your immune system will flare up for weeks if not months. Not worth the risk. Many people think that if you get glutened, the only effect is a bad stomach for a few days, and they just don't understand it's far, far more than that. I would just tell her that you thought about it and researched more and decided it's not worth the risk.
I personally bring my own food. I don't ask. I tell friends and family ahead of time that I can't eat what they're preparing, and I'll bring my own. I'm very polite about it, though. For instance, at Christmas, I had a family member (who I don't see often) set aside some pork chops and not put gravy on them for me. (I didn't know they were going to do that.) I smiled really big and thanked him for thinking of me, but I told him that since I'm effected neurologically, I can't afford to take chances. Even a crumb, etc., etc.
Oh, an example of the risk of eating in a mixed kitchen. After my diagnosis, I had someone help me to get rid of all the gluten that was left in my kitchen. I had been gluten-free 10 weeks at that time. I didn't touch the flour bags or wipe down those shelves, but I was in the room. And I washed my hands a lot. Somehow I got mildly glutened. I think the flour poofed, and it drifted onto my lips or maybe onto something I used to prepare food later. I don't know. But if your host is making your food right after using flour, your food could be at risk.