The London meter maid who inspired the Beatles song "Lovely Rita, Meter Maid" has retired after writing tickets for 19 years. Meta Davis, now a 65-year-old grandmother, says Paul McCartney came up to her one day in 1967 as she was writing out a ticket for his car. "He saw that my name was Meta and he laughed and said, 'That would make a nice jingle. I could use that.' We chatted for a few minutes and then he drove off. I didn't think any more about it, but then later the song came out. My children were big Beatles fans and it was a bit of a thrill for them," said Davis . . .

Mila Mulroney, 32, wife of Canadian Prime Minister Brian Mulroney, gave birth to a 7-pound, 14-ounce baby boy yesterday afternoon at Ottawa General Hospital, a Canadian Embassy spokeswoman announced. This is the couple's fourth child and third son. The prime minister said of his newborn son, "He's loud enough to be a Tory" . . .

A McLean youth, Sean Foley, 17, was fined $500, placed on five years' probation and ordered not to attend any Grateful Dead concerts by a Texas judge yesterday. Foley was arrested when he allegedly became violent after using LSD at a Dead concert. He pleaded guilty to a possession charge . . .

Robert Neuman, longtime Washington political operative, will soon return to his old stomping ground to become administrative assistant to Rep. Morris Udall . . .

Humorist Erma Bombeck was named grand marshal of the 1986 Rose Parade yesterday. "For a woman who started a career at 37 and up until that time made her living sorting socks, this has got to be the most exciting moment I've ever had," she said at a ceremony announcing the decision. Bombeck said she'd hoped to be named Rose Queen but decided, "I just couldn't hold my breath or my stomach in for two hours."