The poem explores, without self-pity, what it is like to be the loser at the game of love.

Throughout the poem, the speaker uses the metaphor of the card game to describe her luck at love. She uses the queen of hearts as her metaphor for love itself. The poem's speaker pictures herself at the card table, where, no matter how hard she tries—through playing fair, cheating, and even dropping the queen of hearts on the floor so nobody else can find it—the queen of hearts, love, eludes her.

Rossetti also uses the poetic device of apostrophe, or addressing a person or object that can't answer back. In this case, the speaker talks to "Flora," a woman who always seems successful at the game of love.

At the end of the poem, the narrator wonders if she does so poorly at the game of love because she has no natural "affinity" for it, implying that she is not meant for love or, in the end, doesn't really want it.

The poem could be read autobiographically, for, though a celebrated beauty who was used as a model by pre-Raphaelite painters, Rossetti saw three serious involvements fail to end up in marriage.

The poem uses a very traditional rhyme scheme of quatrain verses with two rhyming couplets: AABB. Less traditional is a first couplet with ten beats per line and a second couplet with only six.

Thanks for bringing this fine poem to my attention.

The poem seems to be an extended metaphor (sometimes called a "conceit") about the poet's difficulties in matters of the heart (that is, love) and her friend's seemingly effortless success in such matters.

Flora, the friend, always seems to hold the Queen of Hearts, which symbolizes love, or perhaps what we would call today "emotional maturity."  The poet, no matter how much she cuts and shuffles the deck, never seems to draw the Queen of Hearts. 

The poet tells us that once she was deceived by the Queen of Clubs, which appeared to be the Queen of Hearts.  Perhaps this symbolizes a time that the poet thought she had found love, but was later disappointed.

In the poem's conclusion, the poet wonders what her friend's secret is; is it:

skill, or craft, or luck in you:
Unless, indeed, it be
Natural affinity.