Regardless of how uplifting this news article is, I think there is a lot of recklessness on the mother's side. In that condition she should carry an emergency button with her.
Not sure how reliable can a toddler call 911, I'd rather think at a panic button or monitor like other commenters mentioned. But I have another question about this story: how many Alexa emergency calls are jokes/accidental over the entire user base? A few for sure are life saving, but I also expect quite some useless noise.