I don't believe she felt blissful and care free at all. Even if she was guilty I think she would be traumatised by the birth, what she had seen coming out of her body. Childbirth is pretty traumatising, even when you are fully prepared for it, at least mine were. She would be fearful of being caught out. I would be terrified that my mum would suddenly decide to do some gardening, or that my dog would smell something and go digging. She would probably be scared about what was still happening to her body. After my first son I was not at all prepared for how much I would bleed and I couldn't even have imagined the afterpain, it was scary. Even if she planned all this I still don't think she would suddenly feel light as a feather the very next day.
I really don't see how anyone could possibly think they would get away with this. She knew that her doctor at the very least knew she was pregnant, would want to know what had happened to the baby and would ask questions the next time she was there. I just can't see this being a plan carried out with stone cold logic. I've tried to see it from all angles but I just can't get there.
If they can't prove baby was born alive, I don't see how she could be convicted of endangerment. A woman has bodily autonomy whilst pregnant, not seeking care, taking vitamins etc is not a crime. If they can't prove baby was born alive then they would potentially be holding a woman criminally responsible for a still birth and that is a dangerous precedent IMO.