Greek shipping heiress Christina Onassis gave birth to a girl in Paris yesterday. The 34-year-old daughter of the late Aristotle Onassis is married to wealthy French businessman Thierry Roussel, her fourth husband . . .

Oscar-winner Jack Lemmon will be the host of this year's Academy Awards program, set for March 25 . . .

Rockville's Rio Grande restaurant, which first opened on Newark Street in Cleveland Park in 1930, will serve its famous Mexican food to the public for the last time Thursday. When the restaurant was located on F Street, a block from the White House, then-President Herbert Hoover frequently walked over to dine. Then-senators Lyndon Johnson and Richard Nixon also ate at the restaurant. The Rio Grande was founded by Narciso 'Chico' Diaz, 84. He and his wife, Lydia Diaz, 83, are now retired. The current restaurant's site on Rockville Pike has been sold to a developer and is soon to be still another high-rise office building . . .

Those London commoner-columnists are grumbling about Princess Diana. They are saying the young princess is "hard-headed" and "frequently willful." It is on the record that 10 people have left Charles and Diana's staff since the marriage, and one columnist blames the departures on Diana. But Daily Express columnist Jean Rook is the most annoyed, saying that Diana has persuaded Prince Charles to give up blood sports, the strange royal penchant for killing small animals. "Diana makes no bones about the changes she's made in her suddenly thinner, bonier, duller, older, sadder-looking, once red-blooded Charles," Rook writes. "He's now a vegetarian health freak" . . .