This is a lovely item, and for a girl a little older than my six year old may have been ideal. For her however, although she LOVED it and the thought of having her own secret place to write things down, she lost the heart that both opens the diary and makes the secret wording readable on Christmas Day.
We haven't found it and presume it was thrown out with all the packaging, which is sad as this really can't be used without it. Perhaps some thought needs to go into either attaching the heart to the diary somehow, or to have it make a sound when you clap much like some keyrings do. That way it wouldn't get lost quite so easily.
Educationally it has no real value, but it is pretty and girly. If your daughter is around 8 then I would say go for this - any younger and I would consider something else.