Long story short I've been working on a return flight ORD-NRT-SIN on my CO miles for a friend of mine to join me. I've managed to get UA First seats on 3 out of the 4 flights however there is only award availability on UA in economy class for the whole round trip ticket on the NRT-SIN leg that is shown to CO. I have some extra UA miles to burn and was able to book a business class ticket on the NRT-SIN leg so she can join me up front as she will be meeting me in Tokyo. Is this going to cause any issues with her having a ticketed seat in economy and another seat in business? What should I tell the agent upon checking her in at NRT?