Any mother/wet nurse can breastfeed - it doesn't have to be the mother (formula notwithstanding).
Or even pump and freeze for pickup by the outside caregiver if need be.
"My religion requires me to breastfeed my infant naturally."
Even if that worked, it would still only get her something like a 6-12 month reprieve. She's been convicted of murder, none of these ploys will get her out of going to prison eventually.
Might as well skip the middleman and go straight to "my religion requires me not to be imprisoned".
Why not? How is this rule any different than any of the others in a religion?