Hi Helen The piece sounds really lovely, and the combination of colors sounds interesting. Concerning the lone star - There are a lot of Star marks on jewelry. I'm merging your question with star marks on 20th century jewelry. Take a look at some of these submissions there. Your question may have been answered.
Rose gold looks similar to copper, and the stones would need to be tested. They could be glass, simulants, synthetics or natural gemstones. Without testing them, you can't tell. Also a picture helps a lot, and also description of the star. Ie number of points on the star is important when identification star marks.
