The knowledge that she'd been the Moon Princess they'd searched for all that time had hit like a hammerblow, and at the time Usagi had been able to do nothing but collapse to the ground, hiding her face in her folded arms. This is wrong! It was supposed to be Minako!

The feeling never really goes away, even after Usagi lifts her head again and claims her power. Minako isn't the perfect goddess of a Princess that Usagi had imagined, but she is all warrior and all Princess, her power tearing through enemies like justice given form, her words inspiring and commanding the other Senshi in a way Usagi never could. Next to her, Usagi feels like a pale imitation, any light she gives off merely stolen from Minako, and it's only because Minako shines so brightly that she doesn't even seem to notice.

And then Minako shields Usagi in battle like she'd lay down her life for her Princess, or she catches Usagi's hand and says I really admire you, you know? and Usagi's confused/euphoric all over again.