With the OTHER 3DS, take your Rare, make sure it has seeds left, and invite the mii. They'll be carrying the last flower they made, which should be that hybrid. Normally if a mii brings a Rare, it DOESN'T pass on its properties to the seed; it just makes it more likely the seed will also be Rare. But because it's actually a regular breed, it might pass on certain properties, like the Rare stem.