Exactly. What I see on this thread - and it's become quite distressing and emotive to witness it unfold - is a great deal of anger toward women. It's women's assumed job to be default carers. OP is angry with her sister for not assuming that role. People are angry with aunts. Uncles haven't merited a mention. The failure of this poor girl's father to care for her to the extent that Social Services had to step in has passed largely without comment.
It's very easy to become angry with (female) strangers on the internet and to volunteer their time, energy, investment; in short their lives, from the lofty position of the moral high ground. I'd stake a hefty bet that when faced with a similar situation in actual, real life, people would be far less willing to self-designate this task. Easy, too, to insult other women and shame them into assuming the received 'women's role' as carers by stating confidently 'what I WOULD do' in a similar position, when just as clearly, they are not being required to do it.
The thread is obviously hugely distressing and triggering for some posters. The experiences reported on this thread are terrible and obviously life-scarring. No one should have their childhoods stolen and made fodder for adult predilections like this. The PP upthread, who reported her own experiences at the hands of the care system, is right to say that society persistently closes its eyes to systemic abuse. This is at the heart of the issue here.
There are understandably strong feelings about saving the niece in question from the horrors of the care system. To save one child, ten children, a hundred children, is commendable but makes no difference to the myriad others who suffer precisely because the issue is systemic, and the root of the entire problem is, overwhelmingly, predatory men. (I'm not saying it never happens with women. But look at the statistics). Yes, society does turn a blind eye. Why?
For part of the answer look to Mumsnet; a site with a mostly female user base. Any day you care to mention you can find threads stating victims are lying; they're after money; they're jumping on the bandwagon; they are 'out to get' the abuser. (Cf. the recent thread on Michael Jackson). People will say anything to divert culpability from the male abusers actually responsible. Sexually predatory males are excused at all costs whilst society pulls out all the stops to blame women for their behaviour. I see it on these threads time and time again.
Until these attitudes change, and change radically, systemic abuse will continue unchecked. And the problem is not women's failure to step up and be the carers 'society' expects them to be. It's the failure of men to stop abusing women and children. Both men and women need to stop blaming women for this and start turning their anger toward the people actually responsible.
The problem is the predilections of men.