YA/Teen Diary style book

Fiction
Teen/Young Adult
Might have been a series (3?)
Yellow cover, Girl with brown hair (and maybe glasses)
Something like "Keep Out! Dont Read!"

help appreciated thx x

Maybe Anastasia Krupnik by Lois Lowry? It's not in diary format as such, but the main character keeps a private notebook and the book includes extracts from her notes. The brown hair, glasses, and yellow cover fit.

Private - Keep Out by Gwen Grant? it's the first of a trilogy and the cover of mine matches your description.

It steers younger, but Dear Dumb Diary starts with that sort of thing.

These also skew younger, but reminds me of the Amelia's Notebook books.