The fact that Anne keeps a diary in the midst of the Holocaust should be evidence that she is not a meek girl. In the terror of the Nazis, hiding in the Annexe, and living every moment as if it is her last, Anne shows that she is not meek. In this condition, mere survival proves that there is strength. She is not meek because her diary acts as a form of resistance.
Another example of how Anne is not a meek girl is because her diary entries illuminate strength in her character. Anne is insightful, passionate, intense, and strong-willed. She is not a conformist. She is not one who simply capitulates to what is expected of her. As a result, she is not meek. This can be best seen in the final diary entry. The full range of Anne's intellectual strength and honor is seen. The words and thoughts she articulates are not reflective of one who is meek:
The former means not accepting other people's opinions, always knowing best, having the last word; in short, all those unpleasant traits for which I'm known. The latter, for which I'm not known, is my own secret.
Anne's honesty about herself is one reason why she is not meek. She is direct and open about who she is and what she believes.
Finally, Anne is not meek is because she is able to embrace complexity and intricacy in her world. At a time when so much is uncertain, Anne does not run away from this. Rather, she accepts it as natural:
...and finally end up turning my heart inside out, the bad part on the outside and the good part on the inside, and keep trying to find a way to become what I'd like to be and what I could be if… if only there were no other people in the world.
Anne's coming of age is one filled with hope, despair, freedom, and fear. Yet, she does not run away from the complexity in all of them. Anne is clearly her own young woman. She is able to embrace intellectual and psychological intricacy and do so at some of the most profound levels of thought. This is not reflective of one who is meek. It is through her strength that Anne's words and being are inspirational to many.
Also, Anne has many great quotes that highlight her character and how she views the world. Her outlook on life is a great reflection on how she is different from other children. Many of those quotes are in a link attached.