The ability to manipulate time is very scary. Rose can manipulate time to the extent where she can kill her enemy from the past without making any changes in the present. This is scary because when she kills her enemy in past, it will never be born in the future.
But that doesn't change the present because it creates another timeline. Here she needs the proper power to break the growing timeline. And, if she doesn't succeed in breaking it. Heaven will try to break it. And doing, it will tremendously attack her.
But there is some difference when it is done through Quantum World. Because the law that exists within Quantum World doesn't match with the law existing in the real world. So, if she kills her opponent through Quantum World, she won't create any timeline.
