Prisons have a duty to maintain inmates in (relative) good health. They can't just let them die because thé treatment needed is too expansive
Tinning is 76 years old. As every old lady she probably has several health issues, the kind that would require specific care from the prison's staff and that could get them in trouble if something would happen to her (like a stair fall for example).
By releasing her, the judicial system get rid of that responsability. She is now the only person responsible for her health. She's 76 so she won't be a threat to anyone. And she's gonna be under surveillance.
Also, prisons are not knowned for being very healthy places so I guess she not gonna be there for very long. Either she's gonna die within 5 to 10 years or she will get very old but not very healthy, to say the least...
Last but not least : your tax-money won't be spent to feed, cure or entertain a baby-killer anymore.
Isn't that good news ?