Lady Mary IS a singular woman. I think gratefully of her from some passages of kindness which passed from her to me, when I wanted kindness most, & the saddest of domestic losses was nearer than I thought or would think. I believe her to be a kind woman--a better if not a higher name than a great metaphysician. Have you seen her books upon the External Universe & Cause & effect? She has high talents--but has not perhaps been operative enough to have done much undone before, altho' quite enough to raise her own name above the multitude. Metaphysicians, & I suspect, poets, shd. live in a cave,--or at least live so, as to form habits of concentration & abstraction. Lady Mary (so her daughter told me) used to waltz until she was tire, & then sit down to write about algebra. Her daughter at once admired & feared her--feared her very much--& nobody else in the world. She seeemed to love--in the clear meaning of love...her father--with no fear in that love. There was love too in abundance, I am sure, between the metaphysician & the dramatist--& Lady Mary used to say jestingly--"We are very much in love with each other". Notwithstanding which, he used by her own account to take up his hat & walk out whenever she began to dissert (she does dissert you know) upon primary & secondary qualities in matter--and she on the other hand was the authority in all domestic matters & would'nt suffer any interference--"What can he know about children? Why he was only a boy when I married him". Just those words! I am certain this time about the syllables. They are unforgettable.
Letter 59 in The Letters of Elizabeth Barrett Browning to Mary Russell Mitford 1836-1854, Volume I, Meredith B. Raymond and Mary Rose Sullivan, eds. Wedgestone Press (Winfield, KS: 1983) pp. 154-155. The "domestic loss" is likely the death of her mother in October 1828.
You have to love the description of Lady Mary waltzing until she was tired then sitting down to write about algebra. That sums her up so well. Elizabeth emphasizes the kindness of Lady Mary in a number of places, as well as her rather intimidating character. As she puts it more than once, Shepherd was simultaneously kind and terrible:
Lady Mary Shepherd is a kind & cordial woman--& I admire her talents & conversational eloquence. But she is 'terrible' notwithstanding, without the intent to be so--& whenever I used to like to hear her talk, it was always under the proviso, that she did'nt talk to me. And I have know
gentlemen shrink away from her, from a mor definite fear than mine--for fear of being examined in metaphysics!!--Yet, I admire & like her--& the strongest remembrance I have of the short & distant period of our acquaintance is a grateful one. She once gave me sympathy when I needed it.
Letter 36 (p. 83). This all accords with what we know from other sources.