I would take into consideration whether you need both vehicles. Take into account that her car will devalue, it may incur problems as a result of standing for a year, you'll be paying two sets of insurance, two sets of tax etc. You may be better selling her car, or if you have the space, store it and declare it off the road. You can have her car registered in her name, whilst insuring her car with you as the main driver. Alternatively, see if the insurer will let you add her car to your policy.