What does the definition Browning's love in "Sonnet 43" suggest about the character of the person to whom the poet is speaking?
I suppose one can make assumptions about the object of Elizabeth Barrett Browning's love based on what she compares the depth of her feelings to.
Her lover must be spiritual, to appreciate the comparison of her love for him to her love of the grace of God. Her lover must appreciate the the beauty of everyday life. Her lover is just and honest. Her lover's reciprocation of her feelings has erased her past disappointments and former passions, so he must be open and giving.
She wrote this sonnet (along with the others in the series, "Sonnets from the Portuguese") to her husband, Robert Browning, during their courtship. It is a beautiful testament to the depth of their love for each other.