I wonder if she is now (in interrogations) doubting that the baby was truly dead. This line of questioning would lead me to think maybe I was wrong, even tho I never felt a heartbeat, heard breathing, saw movement. But she held her for quite some time if I recall correctly, and a living baby would have had some reaction in that time.
I seriously doubt she purposely killed a living baby, the more I think through this. For me, it is burying the baby and keeping the birth/burial secret that is her crime.
ETA.... the only plausible explanation I can come up with if the baby was alive is that she "held her too tight" (against her own body perhaps, if we pay attention to her body signals during the questioning) and the baby was smothered. Tho she never says she heard any real signs of life after removing baby from toilet area.