A new side of Fawn Hall was revealed to the world yesterday. On her second day of testimony before the Iran-contra committees, she sassed senators and contradicted congressmen, exposing a hard edge that few would have predicted.

"{On Monday} she was portrayed as somebody who was flowerlike and delicate, not to be pushed or tested too hard," said Sen. William Cohen (R-Maine), one of those who tangled yesterday with the 27-year-old former secretary of Lt. Col. Oliver North.

"But if you scratch the veneer, what you get is solid wood. You know the term 'sabra' -- tough on the outside but sweet on the inside? I think Fawn Hall is an 'arbas' -- sweet on the outside but tough on the inside."

Sen. Orrin Hatch (R-Utah), who praised Hall's "candor" during the televised session, said she was not to blame if she betrayed a bit of ire. "Clearly, she is a very nice woman, very intelligent, very loyal and very strong-minded," Hatch said. "I think that loyalty, that intelligence, made her stand up and say, 'I'm not going to take any guff from you people.' And to be honest with you, I say, 'Hooray for her!' "

In Cohen's exchange with Hall, the two debated whether her former boss should have received immunity from prosecution. When Cohen argued in the negative, Hall, herself testifying under a grant of limited immunity, said, "I think that Colonel North is first a U.S. citizen and he has the same rights that you yourself do, sir."

" ... I don't think anybody's entitled to immunity," Cohen persisted.

"Yet the idea is to complete the investigation. Then why not grant Colonel North immunity?"

"Well, if he would not engage in any wrongdoing, Miss Hall, then we wouldn't have to be involved in the question of immunity at all," Cohen replied.

At which point she cut the senator off. "We have our separate opinions, sir." That ended the discussion.

Hall also talked back to Sens. Warren Rudman (R-N.H.) and Sam Nunn (D-Ga.) and was clearly irritated, judging by her tone, with questions from Rep. Louis Stokes (D-Ohio). "Her irritability was certainly detectable," Stokes said.

When Rudman pointed out that she had concealed documents from the FBI, not the KGB, Hall snapped, "That's true, sir, but we do, in this country, have a tendency to have classified documents get on the front page of The New York Times ... " At another point, she scolded Nunn, "I wasn't solely a fanatic about Colonel North. I believe and admire him, and I am a grown-up, and ... I can form my own opinions and morals."

Cohen acknowledged that much of the questioning was in the kid-glove category.

"I know people were walking fairly gingerly around the edge," Cohen said. "That's the worst sort of sexism, I suppose -- not to treat this woman as a person to test her testimony ...

"Obviously the members were concerned. They didn't want to appear to be taking a person who at first seemed quite delicate, and bully her."

As for Hatch's comment on her candor, Cohen said, "I think she was candid about the things she wanted to talk about, less candid about the things she didn't want to discuss. I think what came through was a sort of moral righteousness about the cause."

Cohen said he wasn't irked by his exchange with Hall. "I was frankly pleased," he said.

"In terms of her dedication and loyalty and tireless work, she'd be terrific," Cohen said when asked if he'd want someone like Hall working for him. "But I would also want to have someone question me ... You know, 'Hey, wait a minute, do you think this is an appropriate thing to do?' "