You may say what you like, but I stand by my choice of words.
Perhaps monster is harsh, but mother does not seem quite right either. Doesn't a woman actually have to give birth to be a mother?
Nitpicking aside, I agree with what you wrote: She did kill her own baby, and she did so deliberately. That fact remains, regardless of what one may choose to call her.
The article (and the associated comments) left me cold. There is something, well, creepy about the way the author describes her decision. I try to empathize, but simply cannot imagine acting that way.