There's no death sentence in The Federation and - for a reason I can't quite put my finger on - I doubt she received life imprisonment.
I didn't advocate for a death sentence, just someplace more like prison and less like a vacation club. Recognize that her sabatoging the communications resulted in the deaths of several of her kidnapping victims that could have been saved with outside help.
The Federation had a death sentence for landing on Talos IV. I don't think they repealed it.
Keeping people in prison is expensive and if she's no longer in a position to re-offend they'd probably let her out on supervised probation. Just make sure she's not in charge of a colony ship.