Date: Early 2000s.
It was aired on the Hallmark Channel.
A young boy either lives with his aunt or visits her for the summer. There is another woman living with her, who seems mentally disabled, she probably doesn't talk. She draws a lot.
The accepted story about her is that she nearly drowned in a lake and sustained brain damage.
But It turns out that a guy (close to the family or a family member) held her underwater because she accidentally (?) witnessed how he killed her boyfriend via hanging or burning.
The murder had a racial motive, the boyfriend was black and the guy was probably a member of the Ku Klux Klan.
After he is exposed he tries to kill her, there is a chase segment at the end of the movie that takes place in a town fair.
An unrelated piece of information is that the boy borrowed his aunt's bicycle and other boys mocked him for riding a woman's bike.
If you Google the plot, you might end up finding somebody else's question about this movie from 2017: