Cheri Olvera, 34, filed her lawsuit in November 2008, claiming Giles failed to provide financially for her and her daughter while she tended to his business and personal needs.
She testified that Giles left a Padres Christmas party in 2007 and picked her and a girlfriend up from another party and started "driving like crazy'' toward their home a short distance away.
Once at their residence, Olvera said, her friend was scared and wanted to leave.
Olvera testified that she got in a Mercedes-Benz that Giles told her belonged to both of them.
When she started to drive away, Olvera said Giles jumped in front of the car, then ran back to the driver's side of the vehicle.
"I was pulled out of the car and hit the ground,'' Olvera testified. "It happened so fast.''
According to Olvera's lawsuit, she and Giles were in relationship from 2003 to April 2008. They got engaged in December 2005, but the wedding was called off because, according to Olvera, Giles would not undergo counseling.
Giles' attorney, James Scott, said in his opening statement that Olvera refused to sign a prenuptial agreement and was out to get "millions'' from the ex-ballplayer.
Giles, a two-time All-Star, retired last year after playing 15 major league seasons with the Cleveland Indians, Pittsburgh Pirates and Padres.
He earned $9 million in his last year of playing, in 2009.
The palimony trial could last up to three weeks in the courtroom of Judge Jeffrey Barton.