In the ballroom at the Annapolis Hilton last week, hours after Del. Lorraine M. Sheehan got a surprise appointment from Gov. Harry Hughes to be Maryland's secretary of state, she suddenly found herself face to face with her longtime adversary and rival Sen. B.W. Mike Donovan, who represents Sheehan's district in Prince George's County.

Donovan and the county's Democratic political power brokers had dumped Sheehan from the party ticket during last fall's elections, but she won a third term anyway over their candidate. Now, Sheehan had one-upped Donovan again, getting the governor's nod for the cabinet post, a job that Donovan had campaigned for and "wanted in the worst way," according to one colleague.

As is her way, however, Sheehan did not back off from the encounter with Donovan. Few words were exchanged, and no congratulations were offered, Sheehan recalled. But Donovan, clearly miffed with Hughes, did tell her he didn't blame her for accepting the position. A few days later, in an effort to "try to make peace," Sheehan said, she called Donovan's office to invite him to her confirmation hearings this week.

"The appointment is made, and I don't think it does either of us any good to continue the battle," said Sheehan, a product of the county's "old-girl network" who rose from the grass roots of local Democratic politics to become one of the most effective women in the State House.

In the governor's cabinet, Sheehan will not be "saddled with some of the pettiness and chauvinism of Prince George's politics," said former County Council member Ann Lombardi, who described Sheehan as a feminist advocate who "plays for keeps."

"She isn't going to make a speech for just being on a side of an issue," Lombardi said of Sheehan. "She is going to try to make it happen."

Lombardi said she thinks it was an "absolute stroke of genius" that Hughes picked Sheehan out of the blue for secretary of state, a job Sheehan herself admits she had not sought and was surprised to get.

But some Prince George's senators, who had given Hughes their own list of candidates (including Donovan but not Sheehan), are still smarting over the way the governor made his decision.

The way the apointment was made was a "typical example of Harry Hughes screwing up everything," said Sen. Thomas V. Mike Miller. Miller said he thought it was "just preposterous" the way Hughes had his appointments secretary call Sheehan and suggest she add her name to the list for secretary of state.

Sheehan is a "nice, capable person," said Miller, who added he would give her credit for being an independent thinker. But he complained that Hughes was "bypassing elder statesmen of the Democratic Party" when he selected her.

As for Sheehan, the attention that has centered on her selection, and the griping, have not deterred her. "It's kind of fun," she said.

As secretary of state, Sheehan, 45, who lives in Kettering with three of her four children, will more than double her salary, from $21,000 as a member of the House of Delegates to $45,000 as a cabinet member.

A native of Manchester, N.H., where she graduated from high school, Sheehan came to Prince George's in 1963, where she raised her family of four children. In 1972, she began working as a legislative aide to former State Del. Craig Knoll, a part-time job that Sheehan recalled paid $50 a week "and all the hot dogs and chicken noodle soup I could eat."

Elected to the House herself in 1974, Sheehan has been a member of the Judiciary Committee, is currently a member of the influential Ways and Means Committee and has been vice chair of the county's delegation.

She will assume a list of tasks that are mundane compared with the rough-and-tumble action of the eight years she has spent in the House of Delegates. Among other things, Sheehan will be keeper of the state seal, supervisor of the Maryland Manual (an annual "Who's Who" in the state government) and signer of a lot of official paper.

More important, however, Sheehan envisions her new post as an inside seat with Hughes and a wide open road to statewide exposure, both of which may spark new ambitions in her.

"This is the governor's last term," Sheehan said when asked what her new job meant for the future. "I'll be watching candidates for governor very carefully."

Will she run for governor? "I don't know that I would start with governor," Sheehan said. Lieutenant governor? "You'd have to see what would happen, but that certainly is attractive."

As the story goes, Sheehan got her start in 1974 when then-Sen. Steny Hoyer, now a congressman, was looking for a candidate to run for the House from the then-new 26th District in Prince George's. The spot on the ticket went to the party worker who delivered the most newsletters in the new district for the incumbents, and the winner was Sheehan. She now represents the 25th District.

In the State House, Sheehan became a vocal advocate of issues involving the mentally retarded and the handicapped, was a member of the women's caucus, and pushed legislation that would make it easier to prosecute rapists and sex offenders.

In 1979, Sheehan, who describes herself as a pragmatic feminist who knows when to pick her battles, has been a floor leader for the pro-choice advocates during the past four years on the abortion issue. She was on Hughes' side in a bitter fight that ended with a narrow vote to continue Medicaid-funded abortions for poor women.

Meanwhile, these days in Annapolis, the Prince George's senators are still smarting about Hughes' choice of Sheehan over their suggested list of candidates. According to one legislator, there are three theories about why Hughes did it:

The first is that Hughes' wife, Patricia, likes Sheehan and that's why she got the secretary of state's job.

The second is that the appointment takes Sheehan out of an intense fight about ending the Metrorail Green line at Branch Avenue instead of at Rosecroft Raceway. (There are those who say that Sheehan, who favors the Branch Avenue route, was bounced from the slate last fall by pro-Rosecroft forces behind the Democratic leaders. Sheehan says she told Hughes she wanted to continue her Metro fight when she becomes secretary of state and that he said "he didn't see why not.")

The third, and most popoular, theory is that Hughes was "tired that he was looking in the bag to the Prince George's senators theory" because it appeared Hughes had bowed to their wishes on too many political appointments.

There is another theory, according to this legislator, which is not on the list but which may explain it all. That is that Hughes said to himself, "Hey, I'm governor and I like her and I think she ought to be secretary of state."