The accident happened on I-45 before Paramatta. The highway shut down for almost five hours overnight.
Deputies say the woman parked her SUV on the side of the freeway, turned on the hazards and stepped out into the road.
"We did find some notes indicating she wanted to harm herself, suicide notes basically, apologizing to family members, saying she was sorry," said a deputy on the scene.
Harris County Sheriff Ed Gonzalez tweeted this morning: "We must talk about suicide" to better understand and prevent it.
"It's just something we need to pay attention to," Gonzalez told Eyewitness News. "We had approximately five suicides over the weekend. I received a call about another one this morning. It happens quite frequently in our county. Over 500 happened last year. That's over 1.5 per day. We see them as young as 9, 10, 11 years old."
In 2018 this time last year, 92 people committed suicide in Harris County. So far this year, 78 people have taken their own lives in Harris County.
The driver who hit and killed the woman, stopped and spoke with investigators. Her grandparents told Eyewitness News she was shaken up but not hurt.
The sheriff's office has notified the woman's family.
SEE ALSO: National Suicide Prevention information: Get help here