I think what is happening here, a bit, is that we're looking at the fact that Lyric's parents were drug addicts that spent time in jail and who did not have primary care of their daughter. We know that Lyric was being raised by her grandmother. From here, maybe it's easier to think that Lyric was generally unsupervised, or that it was more likely for her to push the boundaries. That may well have been true of Lyric, but Elizabeth was in a completely different situation. She was living with two solid parents and three siblings. She had a normal life, attending church, going on family vacations, enjoying a happy childhood. A major factor that would influence her decisions to behave, or to do the ooposite of what was expected of her, would be her mother's health (I think). There is no reason to think that she would completely misbehave when her mother is at the doctor and her grandmother has to leave soon. I think we might be vulnerable to projecting assumptions about Lyric (based on her parent's history) onto Elizabeth ... but if we don't do that, if we see Elizabeth as a responsible young girl that wanted to make her parents and grandmother happy, there's no reason to assume that she would simply take off for a 30 minute, two mile bike ride without telling anyone what she was doing.