I have someone that would like me to make a cake with a miniature plate (cake topper) made in gumpaste that matches one of their favorite china patterns. She has specifically asked me about copyright issues with china patterns.

Has anyone ever run into any copyright issues, or know where to begin asking questions? Can I modify the design slightly and take the risk of infringement away? Thanks for taking the time to respond!

I've asked for permission for lots of things. All you have to do is contact the manufacturer of the item and ask permission to replicate the design. Tell them what it will be used for.