She is Jeyne Poole, friend to Sansa and daughter of Winterfell’s deceased steward (I: 58). After Littlefinger took her into his custody, her fate was unknown (I: 456). There was some concern that, given his ownership in brothels, that she was destined to become a prostitute. However, it seems Littlefinger was more devious, as he realized that with Arya Stark missing having a young girl roughly of an age with her and familiar with Winterfell and he North could prove useful. This appears to be confirmed by Cersei’s remarks where she states, "that she was actually some stewards whelp tricked up by Littlefinger." (IV: 248) A Dance with Dragons fully confirms this, and reveals that Littlefinger’s taking her into his custody did in fact include her being sexually victimized so as to better “please” her husband-to-be (V: 499).