Chitoge is very smart and completely fluent in both English and Japanese despite growing up in America, she is half-Japanese. She is somewhat forgetful, aggressive and quick to attack someone who gets on her nerves. Once you get to know her though, she becomes very talkative and nice.
She is very bad at cooking due to the fact that she never measures ingredients along with adding in random things she thinks will make the dish taste better. She is also very athletic as she can easily jump over the school's walls and swim 25 meters in a couple of seconds.
Ever since she was a child she has had a hard time making friends as they were all afraid of her gangster family and as a result she had a cold demeanor towards people at the start of the series due to Claude's over protectiveness. This led her to create notebooks filled with information on classmates in an attempt to make friends.
(Source: Nisekoi Wikia)