Allergy to nickel in my white gold ring

Hi all! I was wondering if anyone has had a similar problem that I am having. I got engaged Christmas Eve last year (2018) and was wearing my ring for about 6 months or so before my finger started to break out into itchy bumps. I have a nickel allergy and until this happened, I had no idea that there was nickel in white gold. I dealt with it for a couple months, until maybe a month and a half ago decided to take it into Kay to see what we can do. They sent it out to get it re-coated and within a week of getting it back it happened again. Now, I may have to upgrade to a platinum band. We took it in a second time, and the guy said if the ring wasn’t bought as is, it would be cheaper because I could just take the diamond off of my current ring and place it onto a new platinum band similar to my white gold one. Should I get a second opinion? I don’t see why they wouldn’t just take my diamond and set it onto something else, even if the ring was sold “as is” (minus resizing). Any advice would be amazing! I still have about 10.5 months until our day, but want to get this headache out of the way sooner rather than later!