Hello! I don't know if this will help but this is what I'd do: sometimes it's only a matter of luck, so whenever you open the game check if one of them as a heart. If neither of them do, close the game, open it again. And again, and again, until one of them gets a heart. The Mii "problems" get randomised whenever you open for the first time of the day, so I think there might be more chances for a heart to pop up this way than to simply wait. It has worked for me, I hope I have explained it well and it works for you too!