La Comtesse de Paris, Isabelle Orleans-Bourbon, whose husband would be King of France today if things had happened a little differently, came to town yesterday to see the French extravaganza and have dinner with the David Bruces.

Then she's off to Chicago to visit her niece, Dona Maria da Gloria Orleans-Braganza, who is married to Prince Alexander of Yugoslavia. Dona Maria is an interior decorator.

Mme. La Comtesse may not be a queen, prbably will never be a queen ("I think the time for that passed with De Gaulle"). But she carries herself like one. unruffled by a mixup over where the interview would be held, smiling calmly when she found two rival sets of reporters and photographers on hand, she seemed equal to absolutely any social occasion.

And she talked with pleasant easiness to absolutely everyone who came her way: the hallmark of royalty, some say.

When the limousine parked and the chauffeur held open the door, she remained in her seat, finishing her conversation before getting out.

Last October she wrote a bestseller in French, and she hopes to publish it in this country. It is "a family book, sentimental," she said. Her husband Henri has just publish his own book but "that's political."

Apparently all of France is agog, nevertheless, over the revelations. The big news in his book is that DeGaulle once told him he should be DeGaulle's successor, as a king. The news in her book is merely that they were good friends of the DeGaulles.

The eldest of her 10 children, Henri, is next in line for the succession, she said, adding that while there are indeed several other pretenders, "they're Spanish, they're from the Parma line, and the only real one is my husband." Her line and his - they are fourth cousins - both can be traced from Hugh Capet in the 10th century.

She will gladly recite the whole lineage for you, including the offshoots. To her, it's just something one knows, like the multiplication table.