The Female Apostle is an Apostle for the God Hand and the very first shown in the manga, though at first she appears to be just a normal blonde girl that the main character Guts is making love to. Shortly thereafter however, she transforms into her true monstrous appearance, that of an almost mechanical looking beast, before being unceremoniously dispatched with Guts' arm cannon,
History
The Eclipse
Her first chronological appearance is during the Eclipse, like many Apostles she came to Feast on the Sacrifices provided for Griffith's rebirth as Femto, the fifth member of the God Hand. She is not seen clearly until Corkus flees from his attackers after his comrades are slain and eaten by other Apostles. Taking on the appearance of an attractive nude blonde to ensnare her victims, she uses this against Corkus who is already suffering from denial and shock to the carnage occurring around him. Not caring whether or not she is part of his dream or the end of his life, he makes his way towards her embrace, only for her to take on the true form of an Apostle and promptly devour him. After this, she is seen once more with Corkus' head within her mouth ready to swallow it
The Black Swordsman Arc
Later on when Guts is on the hunt, she most likely uses her snares in an attempt to feast on him like any other man. She is shown as a busty blonde once more in a sensual moment of passion with the main protagonist, until she takes on her true form and proclaims to Guts that he fell easily into her trap and just before she attempts to kill him, she informs him that at least he was able to taste a last bit of heaven before he died. Of course, Guts on the other hand reveals that she was indeed the one who fell into his trap and as he shoves his arm cannon down her throat, he blasts a hole through her skull and ends the Apostle's life