Unlike the rest of her family, Tracy has blonde hair. Also, in the trailer she appears to have two tattoos. One is on her lower back. This type of tattoo is effectively known as a "Tramp Stamp". The other is what appears to be a near-vertical line of stars on the back of her neck.
Events of GTA V
It appears she does not have the best relationship with her father as in Michael's trailer he is shown roughhousing her for the T.V. remote. Because of her drinking alchohol, having tattoos, and asking to have boys over for the night at a young age, she is probably a loose child.
As seen in the second trailer of GTA V, she has a confused relationship with her mother, arguing with her, supposedly because of her boyfriend.
Considering the fact that her brother is a redhead and both herparents have brown hair, she probably dyed her hair, as it is blonde.