Saturday at 3 p.m. in a 9-minute and 45-second, family-only ceremony at the Swedish embassy, Christina Wachtmeister, daughter of Ambassador and Countess Wachtmeister became the bride of M. Enrico Monfrini, son of Ambassador and Mrs. Henri Monfrini, the Swiss ambassador of Italy.

Christina, a lively, pretty girl who laughs a lot and turns 28 today, wore for her wedding a Giudicelli of Paris white silk chiffon off-the-shoulder dress, a white orchid in her hair, a Cartier love bracelet and a simple gold wedding brand bought hurriedly by the groom on Friday from Washington jeweler Solomon Schwartz.

For his part, the bridegroom, 33, an international lawyer based in Geneva, Switzerland wore a business suit and wedding band matching hers. He is charming, bright, attractive and rich - exactly the kind of man you want to bring home to mother or have mother bring home to you - depending on how you work those things out these days. Following the ceremony the Wachtmeisters hosted a garden reception for 300 at the embassy.

Aside from guests who were friends of the bride's parents - Deeda and Bill Blair, Jane and Frank Ikard. Bill Crook, Ina Ginsburg, Joe and Susan Mary Alsop, Evangeline and David Bruce, Ardeshir Zahedi and Sen. Ted Kennedy, who popped in for the briefest of drinks, the rest of the crowd was clearly made up of friends of the newlyweds. Most had jetted in from New York, Spain, London, Germany or Los Angeles and were - for the most part - very attractive.

"I haven't commented Deeda Blair, seen so many pretty girls at one party in Washington in a long time.

There was for instance, the Countess Gunilla von Bismarck, great-granddaughter of Otto von Bismarck, who had flown in with her boyfriend, Luis Ortiz, from Marbella, Spain, where she runs a boutique. She's an old school chum of the bride.

Joining the countess from Germany were three of her four brothers - Carl Alexander, Maximillian and Leopold, more affectionately known as Ping, Pong and Bolle (that's German for ball), respectively.

The arrival of the 25-year-old countess caused a near riot among the photographers. She has a mass of Jean Harlow-frizzed-blonde hair (natural, she said) that give her the aura of a marvelous Teutonic cupcake.

Aside from her beaded handbag and bugle-beaded belt, the countess was wearing a short, black dress distinguishable mainly for its plunging neckline and the two necklaces she wore with it - one a lucite rectangle bearing a gold "I" ("for Luis, of course") and the other a tiny solid gold bar inscribed with "Luis." Asked if the gold was real, the countess in a shocked voice replied. "Well, I certainly assumed so, but I would never ask."

Also on hand was the London Daily Mail's super gossip Nigel Dempster, who had arrived, via the Concorde, to write a column. "Peter and I thought we had finally left Nigel behind when we crossed the Atlantic," mused Margaret Jay, wife of British Ambassador Peter Jay, "but it looks like he just followed us right over."

Dempsters' purpose, however, was not to write about the Jays as much as about Christina, who according to Margaret Jay, "has always been something of a prominent figure on the London gossip scene." Titi, as she is called dated Sweden's Crown Prince Gustaf before he was king, and also dated actor Peter Sellers for about three years - a romance that ended, said Dempster, the first night she went out with her current husband.

Dempster was definitely not impressed with Washington social life. "I went to Pisces the other night and I was virtually the only person there. Every time I come here and go to that club it's empty. The only way to have a good time in Washington is to call up Ardeshir Zahedi and invite yourself to dinner," said Dempster, who like most of the Briton's present seemed very keen on dropping Peter Jay's name. "I've applied to be his butler, you know," said Dempster.

Despite all the royalty, Titi's best friend, photographer Maureen Donaldson, chose to stand at the party's periphery talking to Maria Ferrer, the 21-year-old daughter of Rosemary Clooney and Jose Ferrer and a first-year student at Catholic University. "God, I wish Harry were here," said Ferrer," speaking of her 19-year-old boyfriend, Harry Crosby, son of Bing, who as you will remember ended up with Maria's mother at the end of "White Christmas."

Donaldson, meanwhile, had flown in from Los Angeles where she first met Titi through Cary Grant with whom - until three weeks ago - the 31-year-old Donaldson said she had been living for the last four years. "Cary and I are great friends," said Donaldson, "but our age difference finally got to me because I want a baby and I want a father of my children to be young enough to be an active father." But Donaldson added, not only will she be having that baby "within a year,"but will herself be getting married by "next September." Donaldson would not say to whom, but has been dating Warren Beatty, and later told Titi that her wedding would either be held in Rochester or Arlington, Va., coincidentally the home of Beatty's parents.

One of the day's top celebrities was Gunther Sachs, described by one of the Chinese bartenders as "the richest man in the world" but perhaps better known as the once-upon-a-three-year-time husband of Brigitte Bardot.

Meanwhile, Enrico and Titi, a former model, circulated happily among their guests, most of whom cautioned against asking Enrico about his first marriage. Enrico, however, simply said, "Yes, I have been married before and have two children. And my first wife was also a Swede. I guess I just can't get away from them."