You shouldn’t lose NCD. If you insure 2 cars, one in your name and one in your wife’s, Admiral do great multicover discounts. My pal just did it with his car & partners, the price was a huge drop compared to anyone else. There’s no reason for your wife not to build her own NCD. Depends what each insurer classes as multicover. If you’re insuring both cars under your name, then maybe that’s the issue.