Fighting back tears, Smith told a House subcommittee: "I prayed to God to help me."
"I figured the car was going to go its maximum speed, and I was going to have to put the car into the upcoming guard rail in order to prevent killing anyone else," she said.
Finally, her car finally slowed enough that she was able to pull it off the road onto the median and turn off the engine.
"After six miles, God intervened" and slowed the car, she said.
Smith said it took Toyota a long time to respond to her complaints. Then, in a brief, five-sentence analysis, the company told Smith, "When properly maintained, the brakes will always override the accelerator."
Toyota has recalled more than 8 million vehicles worldwide — more than 6 million in the United States — since last fall because of sudden acceleration problems in multiple models and braking issues in the Prius hybrid.
After Tuesday's hearing, Toyota president Akio Toyoda will testify before a separate panel on Wednesday. Toyoda has taken "full responsibility" for the uncertainty felt by Toyota owners, and said in prepared testimony that "I will do everything in my power to ensure that such a tragedy never happens again."
—AP contributed to this report