An 18-year-old woman has been charged with murdering her former employer, the owner of an Arlington dry cleaning store, who was found stabbed to death in the store early Thursday.

Patricia Jean Mawyer of 2310 N. Madison St., Arlington, was arrested late Sunday night on a capital murder charge in the slaying of Edith Miller, 58. Mawyer, who police say worked at Miller's Old Dominion Cleaners last December, is being held without bond in the Arlington jail. A bond hearing has been set for April 29.

Arlington police said they believe robbery of the store at 4036 Lee Hwy. was probably a motive in the slaying, although they had originally discounted that theory. Apparently the initial investigation failed to disclose the existence of a missing bankbag containing three days of business receipts.

Police declined to discuss their evidence in the case.

The shock of Miller's death is still being felt in the Cherrydale shopping area on Lee Highway where Edith Miller and her late husband, Earl, had worked for more than 20 years.

After her husband died in 1973, stricken by a heart attack while in the store, Miller ran the business on her own. It was, by all accounts, a great success. "That place was hopping from 7 in the morning until 7 at night," said Sue Kenyon, an employe of the nearby Cherrydale Veterinary Clinic.

Miller, a hard worker who expected as much from her employes, was a keen participant in community activities. She was active in the March of Dimes campaign, in charity bake sales and was honored by Arlington schools for her help in employing local teen-agers. On her wall were pictures of such famous customers as the late Sen. Hubert H. Humphrey (D-Minn.) and former Rep. Joel T. Broyhill (R-Va.).

Customers and neighbors were used to a high turnover among the teen-age employes at the Old Dominion store. "She was very strict," said one customer.

Among her customers, Miller is best remembered for the quality of her service and her constant attention to their needs. Several said she would stay late so they could pick up their clothes, even deliver them personally in emergencies. "She was most, most accommodating," said a fellow parishioner at St. Andrew's Episcopal Church, where Miller recently was made an usher.

"She was really outgoing, very friendly," said Maggie Kellogg, a neighborhood resident, "Everybody regarded her as special."

Not long ago, Miller installed an electronic eye antiburglary device because of the neighborhood's growing fear of crime. But last Wednesday, Miller, who was working late, apparently unlocked the store door to let in a visitor. "There was no evidence of a break-in," said a police spokesman.