Talla Tarly
Samwell's sister, a girl of Horn Hill under her father's stern rule (book).
The fuller tale
Talla is Samwell's sister, one of the two daughters of Horn Hill the books count and the show condenses, and the household's evidence that Randyll Tarly's doctrine only ever applied to sons. Sam remembers his sisters with uncomplicated fondness — the corner of Horn Hill where he was simply a brother rather than a failed heir — and the show's dinner scene gives Talla the personality the books never had room for: bright, chattering, thrilled by her brother's return and his 'wife,' cheerfully oblivious to the ambush her father is laying across the table, and dressed, she complains, in whatever their mother chooses.
Her small show role has one lovely grace note: it is Talla's wardrobe that dresses Gilly for dinner — a wildling girl in Reach silks, welcomed by the women of a house whose lord will insult her before the meal is out. When Melessa rises from the table in protest, Talla leaves with her; the daughters of Horn Hill, the scene quietly notes, were raised by the mother. She is alive in both tellings, untouched by the wars that have priced her father's doctrine.
The page and the screen
The books give Sam two sisters and no scenes with either; Talla is a name in his recollections, plus a detail the show never used — a betrothal her father arranged, house Tarly's daughters being assets like any other. The show's single dinner appearance is therefore nearly her whole existence on screen, and everything remembered about her — the chatter, the dresses, the warmth toward Gilly — is series invention layered onto a book blank. Nothing in either telling harms her; she is the rare Tarly whose story the wars decline to collect.
Where they stand, season by season
Their fate — if death has found them, it is written here. Open at your peril.
The chronicle records no death for this soul — they are living when the tale leaves them, or their ending is a page the maesters have yet to turn.