In short, Ellie is becoming a menace.
A nice menace, but a menace just the same.
She is quick, and ruthless, and wily, but she still has to keep an eye on her sister when she is invading her sister's space and and stealing her things. Consider this example:
Then she noticed me.
And gave me a "Hey, Mom. Don't tell on me, okay?" look.
It worked. But Margaret has a very finely tuned sense of when her prerogatives are being infringed upon, so although I didn't tell on her, her triumph over the notebook was short-lived.
Her fascination with pens and paper, though, is deep-seated, and so entertaining her can be rather easy.
Of course, it's not always writing. Sometimes she has to get in some time talking to her friends (or business associates) on the phone.