A motorist who struck and killed a Walnut Creek bicyclist last summer has pleaded not guilty to vehicular manslaughter with gross negligence, prosecutors said.

Danville resident Hong Guo, 41, entered the plea Feb. 1. In the late afternoon of June 26, Guo's Honda Civic lost control, and she ran into John Greaves, 44, as he rode his bicycle on Camino Tassajara just north of the Alameda County line.

The Honda also struck a Range Rover head-on. Greaves, who was pinned underneath the Civic, died at the scene.

His widow, Daneil Greaves, is helping to organize a bike ride on Camino Tassajara in Danville for 7 p.m. May 19 as part of a national "ride of silence" in memory of cyclists who have lost their lives in vehicle collisions. She is also following Guo's case closely, after pressing prosecutors to file felony instead of misdemeanor charges.

She calls her campaign "Justice for John."

"I can't bring him back, but there are lot of other things I can do," she said Friday. "I don't think that a felony and being grossly negligent has to be reserved just for somebody who's been drinking and driving."

Daneil Greaves said Guo was distracted and speeding because she was late for a banquet.

"We've all been there — driving fast, making decisions you regret," Daneil Greave said. "I'm going to try to make her an example."

If convicted, Guo faces a year in jail or up to six years in state prison. A preliminary hearing date will be set in March.

Guo is out of jail on $50,000 bail.

For details about the memorial bike ride, visit www.rideofsilence.com.