It was streaky early on - Jankovic won three games in a row to lead 3-1, then Arruabarrena won three games of her own to lead 4-3. But the No.1-seeded Jankovic completely pulled away from there, reeling off six of the next seven games to build a 64 31 lead, and the two went into a holding pattern from there until Jankovic put Arruabarrena away, 64 64. Arruabarrena won the title here two years ago.
"Lara is a hard player to play against - she has a lot of spin and variety in her game, so I just had to work the points as much as I could," Jankovic said. "I don't think I played that great today, but I was just trying to put as many balls in the court as possible and just hang in there. So that's basically it."
Every year, one of the trickiest things about this tournament is the altitude - shots fly. Jankovic was asked about the conditions in her post-match press conference and had a straightforward strategy.
"I feel like when I was really hitting the ball I was making unforced errors," she said.
"I think I need to start stringing my racquets a little tighter!"
Next up for Jankovic is Chanelle Scheepers, who stormed past No.8 seed Lourdes Domínguez Lino in just 53 minutes, 62 61. Beating Domínguez Lino in Bogotá is no easy feat - she has won this title twice.
Jankovic leads Scheepers in their head-to-head series, 2-1, though Scheepers won the last one.
"We haven't played in a while," Jankovic said. "She's a very tough opponent and is playing quite well lately, so it will be a good match. Hopefully I can play some good tennis and get back to the finals."
Scheepers will try to overturn a dubious 0-18 career record against Top 10 players.
The other semifinal will pit No.5 seed Caroline Garcia against No.6 seed Vania King, after Garcia beat Romina Oprandi in 66 minutes, 61 75, and King won a tight one with Mariana Duque-Mariño, 76(4) 75.
King was originally up 5-2 in the second set before letting Duque-Mariño back in - temporarily.
"I was happy to finish off the first set, and then I started the second set very aggressively," King said. "When I went up 5-2 she started playing a lot better, but I'm glad I managed to finish it in the end.
"It was another difficult match here. Every time you go on the court you have to stay really focused, because with the altitude you won't start feeling better every day; I don't think anyone can play too well here because of the conditions. You have to keep fighting. I'm playing well for the conditions."
Garcia and King will be playing against each other for the first time.