Taliana Martinez is a character in Grand Theft Auto V, she is a getaway driver that can only be obtained if the player finds her in the random event Crash Rescue which is triggered by going on the highway around Mount Chiliad and Braddock Pass.
The random event in question is a burning car in a ditch on the highway, the player must give her a lift to Sandy Shores so that she can be patched up, the player must get her there quickly otherwise she will die and the ability to have her as a crew member is lost.
Once the player finds Martinez and picks her up, she will explain what happened (after some persuasion by whatever character picked her up). She explains she was a getaway driver for a gang robbing a pawnshop, and the money was twenty thousand each, the robbery however, was a sting and the gang were chased by cops, two were captured with one managing to get in the car with her. Taliana successfully evaded the cops and passed three road blocks but the remaining gang member pulled a knife on her while she was driving at 100 miles per hour, causing the crash and killing the gang member. 
Taliana Martinez has excellent Driving skills, the bar being nearly full and her composure is very high as well. Her weakest skill is vehicle choice which is still past the middle by a good deal. What makes Taliana valuable as a crew member is that despite her skill, she only asks 5% cut which makes her a perfect choice as a getaway driver for players wanting to save money while also having a good driver.