With Geraldine Ferraro appearing in her first television commercial for Diet Pepsi, one person who isn't criticizing her is Jeane Kirkpatrick.

"I don't know if a legislator's recommendation of a Pepsi is any more relevant than a football player's," the recently resigned United Nations ambassador declared about the ad by the recently defeated Democratic candidate for vice president. "That's a question of esthetics.

"I will not personally engage in public criticism of it," Kirkpatrick said. "Call it sisterhood."

Kirkpatrick spoke last night at American University as part of a lecture series on "Women in the Changing World," organized by Jihan Sadat, widow of former Egyptian president Anwar Sadat. Developing a theme she has sounded often in the past few months, Kirkpatrick said her four years in the Reagan administration had been "a consciousness-raising . . . sensitizing experience" about the role of women in politics.

Ferraro, she said in answer to a question, had been "a viable candidate for vice president." If the former Queens congresswoman now wants to advertise a soft drink "for financial gain," as another questioner put it, "What about those law firms that profit from the presence of former legislators?" Kirkpatrick asked.

"I wonder how anyone would write either a law or a book of etiquette that attempted to prevent legislators in the United States from using their offices for any sort of gain," Kirkpatrick added. "As long as those benefits do not rob the public or are not illegal, then it becomes a question of taste."

Kirkpatrick spoke to an enthusiastic audience of about 700 at the Metropolitan Memorial United Methodist Church, adjacent to the AU campus. She was the third speaker in the series, following appearances earlier this month by former first ladies Rosalynn Carter and Betty Ford.

Sadat introduced Kirkpatrick as "one of the most outstanding women of our generation." She praised her for "standing alone against the overwhelming odds of hostile opinion in the United Nations."

Kirkpatrick said she had also been alone as one of only two women heading delegations to the United Nations. The other female chief delegate, she said, was from Liberia.

In the White House Situation Room, where she met regularly with President Reagan and his top foreign policy and defense advisers, Kirkpatrick said her presence had been as "strange" as that of a mouse she once noticed scurrying across the Situation Room floor.

"I don't think there had ever been a woman in that room before," she said. "The male monopoly of foreign policy had been so complete."

She said she had played a "role-busting role." This caused problems and "double binds."

Before she came to the United Nations, Kirkpatrick said, "Nobody ever called me tough . . . Now I am called 'Ronald Reagan's Iron Lady' in 14 languages and all over the world.

"If a woman seems strong, she is called tough," Kirkpatrick observed. "If she doesn't, she is called clearly incompetent to hold the office. So you take your choices."