Then the next week, she was promoted to the varsity for the Fort Scott High School home meet.
She won again.
And she kept winning. But the FSHS sophomore, who will be running at the Kansas Class 4A State Cross Country Meet in Wamego Saturday, says that it's not been easy by any means.
"It's not easy," Rienbolt said Wednesday afternoon. "It's just something you just go out and do."
She was on the Tiger track team last spring but she ran the 200-meter dash and the 300-meter hurdles. Her first race of this season was 3,200 meters. And as the season goes on, the distance lengthens to 4 kilometers.
Rienbolt said that she went out for cross country to be in better shape for basketball.
"But also, I kind of wanted to try something new," Rienbolt said. "And I've always kind of liked running."
Her first event was the junior varsity race at Labette County. The course there uses the football stadium's track and the football practice field before the runners go out onto a part more like a traditional course. But Rienbolt said she just went out and ran until she felt comfortable.
The next week, Rienbolt was moved up to the varsity. And her first varsity event was the FSHS meet on the course behind the former Cigna building, which is considered one of the tougher ones in the area.
"I was, truthfully, a little worried," Rienbolt recalled about her feelings prior to the home meet. "But I had been running with Paige (Denton) at practice. And she had run the (LCHS) varsity race and got third. I can usually keep up with her during practice and I knew I could keep up with her. But every day is a new day of running and you never know how people are going to run or how you're going to run."
Rienbolt won by a minute. In cross country, that's a fairly large margin. Even over 4,000 meters, the top runners often finish within a few seconds of each other.
The winning continued until she ran in one of the races at the University of Kansas' event at Rim Rock Farm, a picturesque but difficult course. The competition level was also higher as runners from across Kansas and Missouri competed.
"You get there and there are so many people," Rienbolt said. "Everyone has their team set up in their tents. And they've all been there before and know what's going on. And I get up there and I'm the only one from my team and it was overwhelming. There's races going on every 20 minutes.
"So you walk the course and it's just an amazing course. I didn't know hardly any of the teams there. I didn't really know what pace to go at because it was a new course. I just went out strong and I tried to end strong."
Rienbolt tied for third at KU, sharing her place with Caley Shaffstall of Kansas City (Kan.) Christ Prep. They finished behind two runners from Liberty (Mo.) North. She broke the 16-minute barrier for the first time, running a 15:50.
She went on to win the Southeast Kansas League championship. She finished sixth at Regionals as runners from schools the Tigers hadn't seen before -- such as Paola and Anderson County -- plus a couple of experienced SEK runners finished ahead of her.
But between the large gathering at KU and the boost in the level of competition at Regionals, Rienbolt feels she's prepared for State.
"I definitely think it's going to help me a lot for State, just in preparing me for all those people and everything.," she said, particularly about her experience at KU. "I'll be able to breathe and calm down and not be so nervous and know that all you're there to do is run and that's all you can do."
Rienbolt's race Saturday morning will be the very first one of the day, bright and early at 10 a.m. on the course at the Wamego Country Club.
"My goal is to just get out and run like I know I can and just do my best," she says. "That's all I can do."