Anna Seward’s letters were published in the early 19th century; therefore, who knows what might have been removed…, edited out…, changed or otherwise lost.
I can’t say that I’ve come across the original letters — but then I’ve also never really looked for them! Are they destroyed? or in some university archive?? If you know, do let me know.
The first in the series, to the Rev Henry White of Lichfield, dated 7 Sept 1795, is found on Seward’s “visitor” page at present; the others from 1795 — totaling five letters, about or to the Ladies — are found under the new category: Correspondence & Correspondents.
Here is a nice write-up of Seward, at the Poetry Foundation’s website; they include some of her sonnets and poems. A lengthier biography is found at Chawton House Library’s website. Chawton House Library has become a depository for early Women’s Writings; they are worth exploring for writers other than Seward, too.