THERE WAS A TIME when Betty Scharth had her life together, when she worked as a librarian or worked for the post office and earned, with overtime, $18,000 a year. There was a time when she could spend a year traveling in Europe, when she had the peace of mind to paint, to read the volumes lining her bookshelves, to keep her journal, to garden. There was a time long ago when she worked, waiting to get married, and the time that came much later, when she realized that was not to be.

Betty Scharth is 48 now, a woman who has supported herself since she left her parents' home in St. Louis when she was 20. She is a short, plump woman with strawberry blond hair lifted into a bun, and steady blue eyes that mist over occasionally when she talks about what has happened to her. Most of the time her voice is calm, almost analytical, as she sits on the sofa, bundled up in a warm sweater, petting the cat.

Betty Scharth lives in a small brick house in a rural part of Centreville, Va. Her rent is $300 a month and there was a time she could afford it. Now, her house is terribly cold -- 54 degrees -- and after a while she turns on the space heater. That costs less than turning up the furnace and, besides, Betty Scharth is afraid of using up her fuel oil before the winter ends. She doesn't have the money to buy more.

Things started falling apart in July 1977, after she was dismissed from the post office branch in Merrifield because she was unable to operate the computerized mail sorting machines without getting severe headaches. Ability to operate those machines was then a prerequisite to the job. Later, she took an exam to be a clerk-carrier and scored well but the post office declined to rehire her because she had been terminated for cause.

Betty Scharth has asked her congressman, Herbert Harris, to intercede on her behalf and she takes out copies of letters exchanged between the post office and his office. "I can fully understand the rationale for refusing to rehire and employe whose job performance was deemed irresponsible and nonproductive," he wrote Jan. 31. "I fail to see, however, any grounds for denying reinstatement to an employe who is qualified for a position in which openings in the facility exist and the employe's previous work was satisfactory."

Scharth has hope. She hopes that the post office will make an exception and rehire her, that the temporary employment agency will find work for her, that the medical lab she applied to will hire her, that the Virginia State Employment Agency will find something for her. But the phone isn't ringing and she doesn't really know why.

Scharth received unemployment compensation after she left the post office but she says that ran out about a year ago. Last spring she went to work for a real estate consulting agency that folded in August. She has been living on her savings. She is no longer eligible for unemployment and although she may be eligible for short-term emergency welfare assistance she is not eligible for regular welfare programs because she has no dependents and she is perfectly capable of working.

No one knows that better than Betty Scharth. She lists the places where she has applied for work. She has not applied for top jobs, for jobs she is not qualified for, or for librarian jobs, which these days require college degrees. No. She has applied for low-paying office clerical jobs. "There a lot of people looking for these jobs and there are very few jobs that don't require good typing... They all say we'll let you know. We'll get back to you... I'm overqualified. Most are simple, clerical jobs. That's what makes me so angry. I could do these jobs so easily." She doesn't know why the firms won't hire her, but she thinks it may be her age. "Of course they can't say that. They're not allowed to say that because they're not allowed to discriminate. Who knows? Offices for the most part are populated by young girls. Perhaps they think I wouldn't fit in. I don't know, I really don't know.

"It's getting down to the point now that if I don't find something I'm not even going to have enough money to buy gas for the car to go look for a job. My car insurance is due the 15th of this month and I don't know how I'm going to pay it."

Scharth says her savings of about $6,000 has dwindled to about $15 cash. "It's terrifying. My savings are gone now. It was traumatic every time I had to write a check. The longer it went on the more traumatic it became... I've been eating a lot of potatoes and rice and bread and pasta. Sometimes I just eat bread. I haven't had vegetables, fruit or any appreciable amount of meat. I don't sit down and eat a piece of meat.

"I am just desperately hoping that I can find a job. If nothing happens and it would get right down to the crunch, I don't know. It gets so terrifying. I wake up at night sometimes or I wake up in the morning almost screaming in terror.

"At times there's an overwhelming sense of being alone. At times there's a stone wall and no matter how much you beat on it it doesn't crumble even a few grains. It's like no one will hear you. No one will help. Nobody will care. It's like you're voiceless. Powerless. I'm terribly powerless.

"When I was younger, when I was 20, 25 years old, times were so much different. In those times, every girl thought she'd get married and have a family and a husband who would take care of her. I thought that, too. I had a big social life and lots of friends. At that time, the guys I wanted didn't want me and the guys who wanted me, I didn't want them. I never got married."

Betty Scharth worked for an advertising agency in St. Louis from 1948 to 1965, when she quit her job as assistant librarian to travel in Europe. "I wanted a change in my life." When she returned to the United States, she settled in the Washington area, where her brother was stationed, and worked as a librarian for an aeronautical engineering firm, a railroad company and a trade association. When the association decided it only needed one librarian, she collected unemployment and worked at her apartment complex and finally landed the job at the post office in 1976.

There is a desperate quality to Betty Scharth's life now.She has begun to look for jobs as a housekeeper at the same time she is hoping desperately that the post office will rehire her. Friends who might have helped her have moved away and she feels there is no one she can really turn to. She talks of "going under," and knows that something dreadful has happened to her.

She says she feels ashamed and embarrassed. "It's like I was a terrible failure. I haven't committed any kind of a crime or anything like that. It's just when you've been self-supporting all of your life, it's a dreadful thing to admit you got into this situation.

"I have always tended to think of people who can't find a job as being really down, at the bottom of society. We don't think of them as being people who've been places and done things and are bright and are in danger of going under."

Betty Scharth says that these days we are hearing a lot about displaced homemakers, divorced or widowed women who, she says, at least have children to look after them. But what about people like her, women who never planned to have a career, who were never educated to support themselves all their lives?

"The future," she says, is scary for someone like me."