It's interesting that some posters have to lay their own beliefs over this.
How ever it turned out, it is not the OPs fault. The idea that she did it the "right way" because she waited to see if someone saw the baby is a huge judgement. Even if she didn't, she was a traumatised child, most adults would have a hard time dealing with birthing alone.
@Flowerss - I'm so sorry this has surfaced today. It completely makes sense that you dissociated from what happened, or was just too big an event to process. Thank goodness you survived, and recovered physically.
I think you need a proper therapist or psychologist. If you go to your GP, you don't have to outline the exact issue, you can say that your had a life changing event at 14, which you've carried secretly all this time, and has suddenly surfaced. Explain how you're feeling now, and that you feel that you need real help, but not safe to describe to them what happened.
Obviously it's up to you, but I wouldn't go searching for information on the baby until you have a proper support in place. If it is in the papers, the way it's written up might be distressing, just reading it might make it another level of real, iyswim, and until you've started unpacking all the details/ how you feel, it might be just overwhelming.
Without going into detail, I had a similar (but very different) issue going back to the same age, and I finally wanted to go back and see what I could find, and was unprepared for the impact. Obviously you're a different person, but I just wanted to give you a heads up.
Take care, don't feel you have to fix all this, today, at all, just go one step at a time.
Consider, though, you've another 80 years ahead of you. It might be sensible to start dealing with this in some small way, so it doesn't lurk and cause you decades of distress. 