As I've sad before, as international law prevents us from making her "stateless", then unless we can find somewhere else to take her (eg, Bangladesh, due to her mum), we have no option but to allow her back into the country......... and then apply the appropriate legal proceedings, together with suitable rehabilitation treatment.
Well, we could deny it I suppose, breaking international law, but surely, as a mature, civilised country, we wouldn't want "an eye for an eye" on our statute book..... would we?