Barbara Mandel wants the public to know she is not trying to get even by suing her former husband, suspended Maryland Gov. Marvin Mandel, for some $40,000 in back-due alimony payments.

"This is without doubt one of the hardes things I have ever done. I don't do this as a soap opera. I never tried to hurt him," she said yesterday in a discursive emotional discussion prompted by a reporter's phone call.

But, as hard as she says she has it was, in the past few days she has opened through court filling previously secret details of the couple's feuding that will inevitably prove embarrassing and painful to both.

The governor was indeed in a way his head, according to the 1974 aggrement she has placed on public record. He accepted a settlement costing well over half a million dollars while he had a salary of $25,000. Barbara Mandell insisted on even smallest detail in her demands, specifying not only that she would have a new Buick every two years but that it would have air contioning, AM/Fm radio, power steering , power brakes. Her portrait should always be displayed in the governor's mansion, it was agreed.

Barbara Mandell is also suing Irvin Kovens, once one of the Mandels' dearest friends who, with the governor, faces a four-year prison term for potical corruption. He had guaranteed payment of the divorced settlement which Marvin Mandel knew he couldn't afford.

"I thought she was my friend," said Kovens, whose relationship with Barbara Mandel deteriorated long ago. "What I guaranteed, I too care of," he said. "She wound up with everything, anyway. She can go as far as she wants to but its spending good money for bad." The former governor was, as is his habit now, unavailable for comment.

When Marvin Mandel walked out on his wife of 32 years in 1973 to marry Jeanne Dorsey, a 36-year-old St. Mary's county divorcee, it was "the worst thing in my life," Barbara Mandel said yesterday. "What hurts," she said when a reporter called her for comment on the court filings, "is that another agreement is broken. It's enough to have this happen once in your life.

"And where is our great friend Irv Kovens" said Barbara Mandel. "He's not paying it because Marvin Mandel isn't governor anymore.

Kovens said he isn't paying because he doesn't have to. "On basis of trying to collect the money, I don't blame her," Kovens said of Barbara Mandel's suit against her ex-husband. "But he's in a position where he can't pay it. The guy needs time. If we win the appeal (of their conviction), then he'll need less time."

That is another issue being raised in this argument: How penniless is Mandel who has sworn that all of his assets amount to less than $2,000 in cash and his personal clothing? He rents a $650-a-month home in Anne Arundel County, a $300-a-month office nearby and recently spent a two-week vacation in Florida with his wife and children.

When he agreed in December 1975 to his private divorce settlement Mandell had different ideas about his earning power. The settlement, if followed to this date, would have been worth some $500,000 to Barbara about $100,000 more than previously revealed. She received $150,000 in tax-free bonds; was promised two lump sum payments worth over $137,000; the car, a $100,000 face-value life insurance policy, and other payments including alimony at $18,750 a year while hea was governor and $30,000 a year once he went into private life.

Many of these details came out in public during Mandel's trial last summer.

Barbara Mandel's portrait was an issue of some importance in the agreement. It read: "The husband agrees to cause to be displayed permanently in the Governor's Mansion, Annapolis, the portrait of wife as First Lady of the State of Maryland, in the same manner and order as portraits of the other First Ladies of the state.

The car, also, was required to be "a new Buick Electra automobile, or equivalent, euipped with power brakes, power steering, air conditioning and AM/FM radio. He shall arrange for payment of tags, all taxes, insurance (including comprehensive, $50 deductible collision, and $100,000 -$300,000 public liability coverage.)

Even though the divorce did figure in the trial and was crucial to the conviction of Mandel on charges that he accepted $300,000 worth of gifts from friends for political favors, Barbara Mandel refused to testify. She said then, as she says now, that she leads an independent life that has little to do with her ex-husband. Besides, she said, she did not want to hurt him.