Eh, Holmes was 19 when she dropped out of colleges. Despite legal adulthood, people are disproportionately stupid and/or naive at that age. It by no means excuses what she did and I think her sentence was at least reasonable and perhaps too lenient. But I think age and the lack of more experienced people with level heads around her is 1) a
slight mitigating circumstance and 2) partly her own fault.
In short, adult supervision should at least be a consideration. Had she be 17 at the start, a difference of a mere two years, that might seem more clear (to some). Legal adulthood at 18 doesn’t confer some magical maturity and wisdom so we shouldn’t regard it much differently than 25-27.
To preempt arguments that this went on without Sunny for some years after she turned 19: 1) Plenty of people with some experience and maturity could have been in her circle of influence before then and 2) I did say age was only a slight mitigating circumstance.