She knew she would not be able to hold on much longer. Natalie was not strong enough to keep Gale under her control indefinitely.
When Natalie no longer had strength, Gale would easily escape.
That would be terrible.
Using Gale as leverage was just a temporary ploy. What Natalie truly wanted was to trade Gale for Joshua. The person she wanted to abduct was Joshua! Gale would stay alive, living with the lifelong pain of losing her son.
"Gale! What should we do? You can't get hurt!" Peter was