He calls her "Mouse," she calls him "Eisie" and, says a friend, they talk by phone all the time when she's back home in California.

Which just goes to show you what one picture can be really worth, especially when it's Alfred Eisenstaedt's famous 1945 VJ-Day photograph taken in Times Square and she was the tiny nurse in it being kissed by the sailor.

"Some people say it's my most memorable photograph," said Eisenstaedt last night, who has taken thousands of memorable photographs in his lifetime as one of the century's most famous photojournalists. "That girl," continued the 82-year-old Eisenstaedt, a trace of excitement showing in his voice, "is here tonight."

"That girl," as it turned out, is Edith Shain of Beverly Hills, 62, the long-ago Times Square nurse who finally worked up the courage in the last year, after 35 years, to writer Eisenstaedt asking for a print. He not only obliged her, he hand-carried it to California.

"Into my own living room," said Shain who showed her gratitude by taking Eisenstaedt on a tour of Los Angeles, stopping for refreshments at McDonald's. "Can you believe it, he'd never been in one."

Last night she was here for the opening of "Eisenstaedt: Germany," at the National Museum of American Art, an exhibition of 93 black-and-white photos taken by Eisenstaedt to contrast the Germany of today and 50 years ago.

"He's just a very gracious man," said Shain, twice divorced and teaching kindergarten these days.

"They are at least very close friends," said Muriel Nellis, author of "The Female Fix" who became a friend of Shain's when both were on the television show To Tell The Truth." "He calls her 'Mouse' and she thinks he's one of the dearest and most thoughtful people she knows."

Underwritten by United Technologies Corp. (UTC), the exhibition was the outgrowth of Eisenstaedt's first working trip back to Germany since leaving there in 1935. As desribed by Alexander M. Haig Jr., president of United Technologies, the project was a contribution to German-American culture. UTC also does $230 million business annually in the sale of airplane engines, helicopters, air conditioners and electronic equipment in Germany.

"We have a special feeling for American-German relations in an era where that partnership is so vitally important to the West at large," said Haig, former NATO commander and White House chief of staff under Richard Nixon and recently mentioned as a likely candidate for secretary of defense in a Ronald Reagan cabinet.

In fact, Haig cited the National Security Act of 1947 prohibiting a professional military man from serving as defense secretary (Congress later made an exception for Gen. George Marshall). And although he was at the debate in Cleveland between Reagan and President Carter Tuesday night, he said he wasn't looking for any jobs. "I've got one and it's a good one."

Guests included German Ambassador Peter Hermes and Mrs. Maria Hermes, Smithsonian secretary S. Dillion Ripley, assistant secretary for history and air Charles Blitzer, NMAA director Joshua C. Taylor and some 200 others, many of them Time-Life colleagues of Eisenstaedt. Tonight 900 guests are expected to attend a second reception.