The instinct at the time was to close ranks and keep schtum. The Kerry Babies issue shows that the GardaĂ investigation was ham-fisted at best and malicious at worst. The tribunal afterward was a classic case of the judge whitewashing the GardaĂ at the expense of Joanna Hayes and the Hayes family. Basically a cover-up.
The boyfriend came out to say he had had sex with Ann Lovett from when she was 14, but there have been no DNA tests done since to say for sure whether he was the father or not, and it's not clear why the bishop would be swearing him to silence. Maybe he just wanted to protect the family who were good parishioners, maybe that was standard practice at the time, I don't know and don't claim to know.
Even "being let down by family, community and church" doesn't ring true to me. The alternative to giving birth in the grotto was probably the Magdalene Laundry; and it wasn't just one girl who was "let down" in this way as you delicately put it, it was hundreds or thousands.
So there seems to be a lot we don't know, and I don't know how you can say "It was investigated." with any degree of confidence, seeing as how most people in Granard maintained an omerta, the instinctive tendency at the time to cover up, and no Garda, Health Board or Dept of Education report was ever published. And if there was a Garda investigation, what makes you think it was any better than the Kerry Babies investigation?