Just her personality?

My friend and I had our children three months apart. My daughter is 9 months old and hers just turned 1 year old. She acts like there is something wrong with my daughter because she is calm. (Trust me, she's a handful and cries and has little fits just like any other baby!) My girl is not interested in playing with her daughter, she's actually kind of scared of other babies. My daughter is very playful and loving and she loves talking to me and her daddy. She's developing perfectly says her Pediatrican. Her daughter is very rambunctious and is constantly yelling and hitting. (She has been doing this since she was 6 months old) She makes me feel like I'm doing something wrong because my daughter isn't like that. Surely I'm not alone with having a baby like this? it is just my daughters personality?