A Downingtown teen driver was text-messaging and speeding on her way to make a marijuana delivery when she caused a fatal accident in April - a prime example of the dangers of cell-phone use by motorists - a Chester County prosecutor said today.

"The facts of this case are extremely disturbing," Chester County First Assistant District Attorney Patrick Carmody said. "It's fortunate more people weren't seriously injured."

Police said Meghan L. Obendorfer, 18, was exceeding the speed limit on rain-slick Creek Road in East Brandywine Township about 4:30 p.m. on April 14 when she failed to negotiate a curve and slid into the path of a school bus in the opposite lane.

Obendorfer's passenger, Nicolette Pomon, 17, of Downingtown, who was nine months pregnant, was pronounced dead at the scene; a certificate of fetal death was issued to her nearly full-term baby daughter, police said.

Steven Dilworth, the driver of the school bus, which did not have passengers, was treated for minor injuries, police said.

"Personally, I think Pennsylvania should follow New Jersey's lead and ban the use of cell phones in cars," Carmody said. "We have a younger generation that is dependent on cell phones and texting; it's unrealistic to expect people to do that while paying attention to the road."

Obendorfer, who is free on unsecured bail of $25,000, is scheduled for a preliminary hearing Monday. Her charges include homicide by vehicle, reckless driving, and marijuana possession. Her attorney, Glenn E. Davis, was not immediately available for comment.

According to the criminal complaint, East Brandywine Township police found two cell phones, one of which Obendorfer had been using, and a plastic baggie of marijuana in her 2007 Chrysler PT Cruiser.

Phone records showed that Obendorfer received 39 messages and calls in the hour preceding the crash, the complaint said. Text messages indicated that she was en route to deliver marijuana to a female juvenile in Glenmoore, that she had a conversation with her mother, and that she was in a hurry, the complaint said.

A draft text message to the Glenmoore girl was started at 4:30 p.m. and was not completed, the complaint said.

Accident reconstruction showed that Obendorfer's average speed was 43 m.p.h. before the impact with the bus, the complaint said. The posted speed limit is 35 m.p.h.

Contact staff writer Kathleen Brady Shea at 610-696-3815 or kbrady@phillynews.com.