Don't tell her what YOU like, pay attention to what SHE likes. Check out the big store AND the small shops - you'd be surprised at how much money you can save with a little patience. You can save hundreds to thousands of dollars by shopping around for stones and mountings. Karat white and yellow gold are basically the same thing. 10k white gold has the same amount of pure gold in it as 10k yellow gold.
Pure gold has a yellow glow to it.
But karat gold is not pure gold, it has other metal alloys in it. If the manufacturer wants the final product to take on a whiter sheen, he simply uses a particular mix of alloys when creating the karat gold. White gold jewelry may seem rarer, but that is only because yellow gold has been more popular these last thirty years or so. Our mothers and grandmothers were very much into white gold jewelry, and its popularity is rising again today. These days, using white gold and yellow gold on the same piece of jewelry is a designer trend, and gives us a more affordable version of the platinum and 18k yellow gold look.