We are already in chapter 5 and she has only killed one person, at this rate she is not going to be able to kill 100 million.
Most likely it will increase over time:
-At the end of the first month he will only have killed one person.
-In the end the second to 10 people.
-At the end of the third to 100 people.
-At the end of the Fourth to 1000 people.
-At the end of the fifth to 10,000 people.
-At the end of the sixth to 100,000 people.
-At the end of the seventh to 1000000 people.
-At the end of the eighth to 10000000 people.
-At the end of the ninth to 100000000 people.