A Redwood City woman has bee convicted of invol untary manslaughter in the shooting death of her boy friend in Yosemite National Park last year. Marsha Ann Savko, 22, contended that the shooting of Dana Lynn Laudensinger, 23, of Redwood City, was accidental. The incident occurred on Oct. 14 ast year. Park rangers said the vic tim was shot once in the stomach with a .22 caliber revolver as he and Miss Savko hiked on a trail near the Badger Pass ski area. According to Asst. U.S. Atty. Tony Capozzi, the evid ence indicated that Miss Savko had handled the weapon carelessly while removing it from a knap sack, causing it to discharge.