Yellow versus white gold is more of a personal style choice than a trend. Most people have a preference for one over the other. Find out what her's is.
Gold rings are in style and have been for quite some time. The beauty and the timelessness of gold make gold rings a very valued gift and fashion item. Wearing a gold ring will never go out of style.
Yellow gold is Always in style. Take a look around Etsy or Artfire online. Some of the crafters do custom work as well so you could perhaps get it more personalized for the lucky recipient. Good Luck!