Diane E. Slabicki, 29, an associate county attorney of Prince George's County, died of lupus erythematosus June 2 at a hospital in Waterbury, Conn. She was a resident of Laurel, Md.

Miss Slabicki was born in Waterbury and grew up there. She graduated from the College of St. Rose in Washington to attend law school at Catholic University.

She earned her law degree in 1974 and went to work for the Prince George's County Office of Law, which handles civil matters for the county, in the same year. She remained with the office until her death.

In addition to her work, Miss Slabacki was a member of the parish-council of the Resurrection of the Lord Catholic Church in Laurel. She also taught confirmation classes there.

She was a member of the American, Maryland and Prince George's County bar associations. She also was a member of the Prince George's County Women's Lawyers Caucus.

Survivors include her parents, Walter and Irene Slabicki of Naugatuck, Conn., and a sister, Denise Carrington of Wolcott, Conn.

The family suggests that expressions of sympathy be in the form of contributions to the Connecticut Lupus Foundation, Box 7-T, West Hartford, Conn., 06107.