Lauren Nelson was on her way to see her boyfriend in San Francisco on Wednesday when the crash happened. She apparently lost control of the SUV at about 8:45 p.m. while driving south on 101 just before the Marin City exit.
Nelson, who worked for an advertising agency in San Francisco, was thrown from the SUV and she might have been hit by another passing vehicle, investigators say. The SUV kept going, flipped over the center median and eventually stopped on the northbound side of the freeway.
Nelson's boyfriend received a text message from her within five-10 minutes of the crash, a CHP officer said. Investigators are trying to get the password for Nelson's cell phone so they can find out the details of her outgoing texts.
Police said Nelson, from Kentfield, was not wearing a seat belt when she crashed. Investigators are awaiting results from toxicology tests.
Nobody else was injured in the crash.