She says she would describe herself as a generally happy person: "I just don't let things bother me." The 40-year-old legal secretary trains dogs in her spare time and lives with her husband, Michael, and son Steve.
Just miles away lived Gena Foster, also a mother - to 15-year-old Brittany, 11-year-old Christopher and Francie, who has cerebral palsy.
Until a year ago, the two had never crossed paths - until an encounter that turned deadly on a busy Alabama highway. Shirley Henson never granted an interview about that night until now, when she shared her story with 48 Hours Correspondent Troy Roberts.
Henson doesn't think she lost control, she said. "I was just so scared. I didn't know how to react. I didn't know what to do."
Henson was returning home from work driving her SUV on I-65, just south of Birmingham. In the car ahead of her was Foster. Suddenly Foster slammed on the brakes of her Pontiac, Henson said.
"I guess she was mad because I was a car length behind her," Henson recalled.
Over the next several miles, Foster became increasingly agitated, according to Henson; she threw a plastic bottle out of her window and brandished what Henson believed was a weapon.
"I turned on my high beams for a second, and she was shooting the bird," Henson added. "I thought, you know, 'She's crazy; she wants me to hit her car.'"
The women took the same exit. When they reached a traffic light, Foster - still in front - stopped her car, got out and headed for Henson.
"I don't remember thinking anything except that she was coming at me," Henson said, adding she believed Foster was going to try to kill her.
Foster didn't run full speed, but she got out of the car and covered the distance in a hurry, recalled witness Jim Hardy, who watched from his car. "She was screaming," Hardy said. "She was furious."
John Farmer also watched. "Ms. Foster got ouof her vehicle," he recalled. "I wouldn't say she was yelling or screaming, but she was talking in a loud tone of voice."
"I knew she was mad; I knew she was crazy," Henson declared. "And I had seconds to do something to protect myself."
Henson reached into the car console for the licensed revolver that she has carried since a stalking incident years ago.
"I looked up, and she was there; her face was in the window," Henson said. "She was so mad," she added, crying. "She said, 'You need to quit riding somebody's ---, you ------ -----!'"
"She kind of leaned back for a second and then thrust her head toward me, lunged at me," Henson recalled. "She spit on my face. And the next thing I knew the gun went off. It just popped," she said, crying. "Then she was gone."
Struck by a single bullet to the face, Gena Foster was killed instantly. Henson didn't think she had any other choice, she said. "I was going to protect myself if I had to."
Moments later, a hysterical Henson called 911. Investigators at the scene called the shooting road rage.
"It appears to be road rage," District Attorney Robby Owens said. "One woman cut another woman off on the highway."
That night, Henson was arrested and charged with Foster's death. "I was so shocked that they thought that I was the one with road rage," she said. "Anger was not a reaction that I felt at all."
But the district attorney insisted Henson was mad: "She was frustrated that this woman would not get out of her way and then escalated it to the point where she pulled out a gun and shot her in the face."
Nearly a year later, Henson was slated to stand trial. She had the distinction of being the first woman in the country charged with murder in a road rage crime.
The victim's mother portrayed the slain motorist as "a sharing, caring person individual." Mother Pat Newell added that Foster was also "a kind person but feisty."
But Henson's defense attorney, David Johnson, insisted that Foster was not the woman that her family makes her out to be. "They're trying to say that Gena Foster was a nice, sweet, lovely woman who never ad any problems in her life." That's hardly the case, he argued. "She has a reputation for being violent and turbulent."
Could Foster have been the aggressor that night? Was Henson simply defending herself?
"She may have been facing a short woman with a big mouth," Newell insisted. "That does not equate to shooting her in the head."
Foster's former husband, now caring for their three children, agreed: "If everybody was shot that had a little aggression, man, we'd be a rare species on this earth."
Henson faced 20 years to life imprisonment if convicted of murder. Her attorneys planned to argue at the trial that she acted in self defense. But the burden would really be on the prosecution to prove one of three things - that Henson started the incident on the highway, that she used excessive force, or that she could have avoided the confrontation.
Assistant District Attorney Randy Hillman maintained that Henson had other choices: to take her foot off the accelerator, put on her blinker or pull off to the shoulder of the road. "But she chose not to," he said.
"Every time I tried to open up space between us, she would close it up again," Henson argued. "Where are you going to go? What are you going to do?"
When asked about the confrontation on the exit ramp, Henson said she felt completely boxed in: unable to back up or pull around Foster's car.
And Henson said she made one last attempt to avoid Foster by rolling down her window to signal for help.
But District Attorney Robby Owens interpreted that move as provocation. "'I rolled down my window,' said the spider to the fly," he said. "If I were sitting there, and I was afraid, the last thing I would do is roll down my window."
Wouldn't it have been just as easy for Henson to grab her cell phone, roll up the window and call the police? "Well, it wouldn't have if she was coming back at me with a weapon, which is what I thought she was going to do," Henson said.
It turns out, however, Gena Foster was not armed.
"You can think now of all the things that I could have done," Henson said. "But I had seconds."
Was this a road rage murder or a case of a woman acting in self defense?
And what would be a fair and just conclusion to this tragedy?
"I'm perfectly willing to take a personal responsibility for what happened. But I don't think I broke any law," Henson said.
Click here to see what the jury decided.