Jewelry = Luxury item (plus, aren't they expensive?! I love the stuff...being at Tammy Stanley's seminar with 50+ other Silpada ladies had me drooling, but I'm scared at the price she eluded to).
Kitchen/FOOD = More Necessity- and compared to expensive jewelry, is more affordable.
I don't know from personal experience, but I'd say about the demo- I'd say- tell her you need to GO FIRST. Tell her that you'd like to do your demo and talk first- so the food can cook while the Silpada lady does her's. People may get busy 'trying stuff on' and then never turn their attention to you. Then make sure you get as much of your booking/talk in while cooking (do some interactive, so you can talk about products, and bookigns, etc, while your customers do the work of prepping the food).
I'd also ask that catalogs not be passed out until that person's turn...so they aren't distracted by the jewelry catalog.
And tell her it gives the Silpada lady their full attention too...try not to make it sound like this what works best for just YOU..Give a good spin for her friend too. She's going to want to help her friend.
When the food comes out of the oven, that's a good way to bring the show back around to you, and/or you can maybe wrap up with your doorprize drawing slips or something.
Those are just my ideas on how I'd try to play it - but I'm sure someone who's DONE this sort of co-party can give you more.