BROCK-Dec. 19, 1999 A candlelight memorial was held on the first anniversary of the deaths of four Brock teen-age girls who were killed in a head-on collision with a pickup truck whose driver was drunk, officials say.  The crash that killed Mandi McWhorter, 15, Lacey Osina, 17, and Staci Lee and Whitney Welch, both 16, happened after the foursome left the Brock school gymnasium Dec. 19, 1998, celebrating a high school baskektball victory.  The Brock school gymnasium was the site of the service honoring the lives of the girls. It was called a "celebration of remembrance,'' by the Rev. Cary Killough, pastor of Brock Baptist Church and organizer of the event.  The tragedy turned the small Brock community into a loving family sustained by God this past year, Killough said.  "It doesn't seem like it's been a year,'' said Mark Osina, Lacey's father.  "It seems like it happened yesterday. We haven't had the trial or anything. Everything like that seems to have been put on hold. But the eternal flame and the service seems like one of the last things we can really do for the girls and that is a comfort to us,'' Osina said.  A program of special music and videos concluded in darkness when a single candle gave out the only light. Then four pink candles flickered in the darkness and soon the entire gymnasium was aglow as candles held by ?? (estimate of the number present) friends and family passed the light along.  Families of the four slain girls took the candlelight to the nearby Brock Cemetery where three of the girls are buried. A marble statue of an angel representing Whitney had been placed at the burial site and the eternal flame was lit.  "We know the girls are in a better place,'' said Lezlie McWhorter, Mandi's mother. "The eternal flame is there to remind up that we'll see the girls again.''  Last year, the honor students left Brock gym to drive to Weatherford to rent videos for the holidays. On their return home along a two-lane roadway about one mile west of Weatherford, their Nissan Maxima was met head-on by a pickup driven by Ricky (cq) Carter of Fort Worth. Carter's blood alcohol level at the time of the crash tested at 0.16, officials said.  The four girls wore seat belts and were traveling slightly under the speed limit, according to Department of Public Safety investigators. Carter's truck speedometer stuck on 83 mph after the crash, investigators said.  Carter was injured but survived and was later indicted by a Parker County grand jury on four counts of intoxicated manslaughter. District Attorney Don Schnebly said Carter is scheduled for a preliminary hearing on Dec. 28. Schnebly said Carter's trial could be set for April.  The families helped lobby for the passage of a bill that lowered the legal intoxication level to 0.08.