I would think that would be up to you to determine as she is soliciting feedback.
And I'm saying it's a stupid (or at least badly worded) question.
In string analysis we postulate a set of "change" operators, which can be just about anything we want (depending on the situation), and we usually look at the
minimum number of changes required to turn S1 into S2.
Of course,
actual changes may vary, because some changes may be made and then reversed.
For the OP, if changes = sentence substitutions, possible answers include 1, 2, 3, and 7000000000. But the sentence is being changed at least once.
If changes = word substitutions, possible answers include 1, 2, 3, and 7000000000. But at least one word is being changed.
If changes = letter substitutions, possible answers include 2, 3, 4, and 7000000000. But at least two letters are being changed.
If changes = moving letters up or down in the alphabet (taking "A" as following "Z"), possible answers include 19, 21, 23, and 7000000001. But at least 19 positions are being moved.
Overall, the answer is "at least one change."