Betsy is an 8-year-old girl, two years younger (and hence two grades below) her older brother Steve. She has long, dark brown hair that reaches down to her shoulders, which she holds in place with a yellow hairband. She wears a royal blue t-shirt, cyan shorts, and blue flats.
Although her stature is shorter than her brother Steve, her face is slightly longer.
Betsy is a kind, intelligent individual, who tends to provide advice towards problems George has gotten himself (and occasionally even herself) into. Unlike her brother, who's often ambitious, Betsy is more easy-going and shows good sportsmanship. Her brother, being in 5th grade, believes he is smarter than her, but this is largely proven false throughout the series as she often outsmarts him in many challenges, sometimes with the assistance of George alongside her.
It is shown that Betsy is in 3rd grade in the series, and is implied to make better grades than her brother. As mentioned before, she often competes in many challenges and contests with George and against her brother, which she and George always win due to Steve's overconfidence and being more mature than he is. While both of the siblings often try to help George with his problems, Betsy does this more often than her brother does, proving she is more helpful and caring.