All your suggestions are so thoughtful. Thank you. I especially liked Jackie's "the one whose protective shell remained impervious to the love I poured over it." Now there's a definition waiting for a word!

Maybe "beloved" isn't such an inappropriate word. In many relationships, the dichotomy is that there's a beloved and a lover instead of the reciprical beloved and beloved. Or Party A may fall out of love before Party B. Party B is left stranded with full feelings that must be gotten over.

Geez, if there isn't a word for such a predicament, there should be!