Answer:
because all the other girls was getting more attention and she needed to do something about it
i would think A? before taking my answer maybe wait for a second opinion :)
I think Mary and Colin´s transformation is gradual. Mary and Colin both become different people. Mary grows up and is less spoiled, and Colin outgrows his mean ways when he goes outside and sees the secret garden realizing he wasn´t injured as previously thought. As for evidence I am currently re-reading the book now.
