Not to be confused with Anne Dalkeith who also became Anne, Countess of Morton. Finding it took some doing (but not associated with the name Wortley), but her article in thepeerage is here. The first image in thepeerage article is similar to this portrait and her older brother, William, was born around 1585.
The Tate's notes follow, "This typifies the British Jacobean portrait formula. The subject appears full length and almost facing the viewer, standing on a rich carpet or, as here, on rush matting, flanked by lustrously painted curtains. There may be an accompanying chair or table, but the artist shows no interest in conveying its spatial relationship to the figure. The costume is meticulously depicted, with an almost hallucinatory clarity.
Anne Wortley's face and hands are painted in a more shadowed manner, associated with Netherlandish-trained artists. The portrait may have been produced by painters collaborating in a workshop, rather than by a single artist."