I think there should be more jail time for such cases, not less.
A baby drowning in a bath whilst the mother is in another room playing with her phone is not an accident.
It is manslaughter.
It is known that babies can drown in very shallow water.
It is known that babies are not strong enough to hold themselves up, roll over etc etc.
It is known that bath seats will not securely hold an unattended baby in the bath and prevent drowning.
Sending a whatsapp, answering a phone, making a call - none of those things are vital, and if you take the phone into the room with you, can be done without leaving the child.
If her baby had drowned because she had turned to grab a towel, slipped and banged her head and knocked herself out for 4 minutes, THAT would be an accident.
She took known, obvious risks, for no good reason and killed someone as a result.
If she gets a 'there there, you'll live with it for the rest of your life and that's punishment enough' what are the chances she has another baby and takes the same risks?
You don't think folk are stupid enough to do that - I can tell you they are. They tell themselves its not their fault, it was an accident, they didn't mean any harm... and go and do it again.