YA or Middle Grade, 90s or early 2000s. A book written like letters or a journal about a circa 13yo blond girl falling in love. I seem to remember that she had 2 sisters.

[Mina]

I remember that the cover looked like a journal, with a green boarder I think, and a photo/selfie of a white haired young girl in the middle. I think it was part of a series. I read a German version but I suspect it was translated from either Danish, Swedish or English.

[Rainbowheart]

Annemaries Tagebuch?

[Mina]

Rainbowheart, das ist leider nicht das Buch, dass ich suche! Allerdings hat es wirklich viele Ähnlichkeiten!

[Rainbowheart]

Haha, I actually don't speak German, so I had to use Google Translate.

"Unfortunately this is not the book I am looking for! However, it really has a lot of similarities!"

I'll keep searching!