Why does Anne call herself a bundle of contradictions?

Anne addresses her self-image as a "bundle of contradictions" in her letter of August 1, 1944. This is just days before she is discovered, captured, and sent to Auschwitz. She explains that she has a "dual personality." On the one hand, she notes her own "exuberant cheerfulness," on the other, she has a "deeper side." We, of course, as her readers, are well aware of this deeper side, though it is clear that she is often lighthearted.
She fears that if people get to know her deeper side, they will not recognize it for what it is, and she suggests that she displays one side—the carefree, silly side of herself—to the world while keeping the more serious, earnest side to herself. Most importantly, it is her more serious self that she sees as guiding her through life, even if she doesn't show it. She goes on to say that she has acquired a reputation as a silly girl, and the fact that she doesn't think anyone can see or appreciate her other side is deeply hurtful to her. So Anne sees her external image as contradictory to her inner self, which she believes is the more authentic of the two. 
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