I was somewhat curious as to that as well.
What on earth makes you think she knows who the father is? This is an unwanted 13 year old girl who was running loose for at least a month with no one looking for her (how long do you think it takes one of the local pimps to get hold of a girl in that situation?), in addition to spending time in group foster homes, where inmates are routinely raped by other inmates, as well as staff. There are probably dozens of possible fathers, most of whose full or real names she never knew.