Chris Evert scored a 2-6, 6-1, 6-1 victory over Sue Barker this afternoon in the final of the $150,000 Virginia Slims Championship. Moments later she confronted the play-by-play commentator for the telecast of her $50,000 victory, in a hallway deep inside Madison Square Garden.

She tugged playfully at the lapel of his blue velvet blazer and smiled impishly. "Did you call me the Hatchet Woman again?" she teased.

But even though Evert, who is gentle and unfailingly pleasant off the tennis court, despises the nickname that makes her sound like a murderess, she knows why it is attached to her.

What separates the 22-year-old Floridian, not only from the rank-and-file of women tennis players but from the rest of the upper echelon, is her mental tenacity; a Lizzie Borden-like obsession that keeps her wielding her racket like an axe in brutal backcourt rallies until whoever is across the net is chopped away.

It was this singular determination, which allows Evert to focus full fury on her opponent and purge all intrusions from her mind, that best characterized today's victory - Evert's 50th in 70 tournaments since the start of 1974, when she became No. 1 in the world.

Evert started slowly and waded immediately into the full force of Barker's forehand, which she says is the best she has ever played against - not only powerful, but beautifully disguised. "I didn't have the faintest idea when she was going cross-court and when down the line," Chris admitted later. "It really scared me in the first set."

But after playing that first set nervously and sloppily, double-faulting four times and committing nearly half of her eventual total of 33 unforced errors, Evert reasserted her concentration. She let Barker punch herself out and won convincingly in one hour 17 minutes.

Evert is first in prize money and first in the rankings, if not always first in the underdog-loving hearts of her countrymen. By the end she had demoralized the plucky, rapidly improving Barker and earned the total respect if not affection of the 11,651 spectators, who were plugged in to the match and vocal in their partisanship.

Both began cautiously. But from 2-2 in the first set, Barker hit a stream of flashing winners and, aided by Evert's surprising lethargy, ran off four games in a row.

The 20-year-old Englishwoman seemed capable of grasping her elusive first victory over Evert in a dozen career meetings. Murmurs of shock and whispers of "upset in the making" filled the Garden. Piercing shouts of "C'mon, Sue" begot equally shrill, but slightly desperation-tinged, responses of "Let's go, Chrissie!"

The crowd's involvement heightened as the match went on, reaching a peak in the fifth game of the final set, when Barker lost her serve a second time to fall 1-4 down. After that a hush grew, and it seemed that everyone in the building could sense, even palpably feel, the psychological domination Evert exerted.

"Even if I don't show it, I think I feel more than most players," Evert said afterwards. "I have a drive inside me, a burning desire to win every time I step on a tennis court.

"I'm not as strong as a lot of the women. I don't have a serve like Martina Navratilova, or quickness like Rosie Casals.My great strength is my mental intensity. That compensates."

She might have added that she doesn't have the forehand of Barker, who is only 5-5 and 110 pounds, but hits from that side like George Foreman delivering a right.

In the first set she was thumping, taking full advantage of Evert's uncharacteristically shallow ground strokes. She pounded on them for winners, forced errors, and clearly unsettled Crissie, who was playing about as raggedly as she ever does.

"At first she was dropping a lot of balls really short, giving me a lot of time to pick my spots and put the ball away," said Barker, who won two tournaments during the 11-week Slims season and upset Navratilova (winner of four, and runner-up to five-time winner Evert in the season standings) on Saturday to finish 3-0 in her round-robin group and earned a berth in the final.

"I should have been more patient but after I got ahead I was a bit over-ambitious. When Chris got on top, she got better and better . . . she kept the ball deep and didn't let me do anything."

In the last four games of the first set, Barker was full of boldness and daring. In addition to the forehand winners, she was hitting backhand scorchers that bit into the medium-fast carpet surface fractions of an inch inside the sidelines.

"I didn't think she could keep up that pace," Evert said, and she was right. After playing a good first game of the second set, forcing Evert to deuce before she held her serve, Barker started to slip from her peak. She began missing by the same fractions of an inch.

From douce in that first game, Barker lost eight straight points. Serving with new balls in the second game, she was broken at love, serving her first double fault at 0-40. She suddenly felt that "the conditions seemed a bit faster, I wasn't as comfortable." The momentum had shifted abruptly.

Evert did not have a break point against her thereafter, while Barker was to hold her serve only twice more, just once easily.

"If only I could have gotton off to a quick start in either of the other sets . . ." mused Barker later, letting a slightly forlorn look finish the sentence for her. But Evert did not let her.

"The first set went by so quickly, I had to keep myself from thinking negatively," Evert said. "I told myself, 'Think of that as a warm-up set and get the next two.'"

She replenishes her well of competitiveness day after day better than any other player, with the possible exception of Jimmy Connors, but was a trifle slow priming the pump today. She felt strangely empty, considering the importance of the match.

"I was nervous . . . not shaking nervous, I just didn't feel any emotion," she said. "It was an effort to run. I wasn't flowing. Sometimes it's good to lose a match because that gets rid of that feeling. But I didn't want to lose this one."