That set up a last-eight meeting with third seed Simona Halep, who saved a match point to beat Sam Stosur 4-6 7-5 6-2.
Although the Romanian has struggled with injury and form so far in 2017, Konta, typically, is not looking too far ahead.
"I'm happy that I'm still here and get to play another match," she said in her post-match press conference before she found out the identity of her opponent. "I don't necessary believe in open fields because every single player in this draw is world class. So every match is as tough as the next.
"I'm just happy to be still part of the event, and whoever I play next I know it'll be a tough game and I look forward to being a part of it."
A much more difficult night looked on the cards for the 10th seed as Arruabarrena, who had only won one match this year prior to arriving in Miami, played superbly in the opening set and only some impressive serving from Konta kept her in it.
And at 6-5 she raised her return game as well, breaking Arruabarrena to take the opener. She timed it nicely as it was the first time she had been ahead in a service game of the Spaniard's.
The second set was a different story, as Konta began to flex her muscles and hit her opponent off the court on her way to a 4-0 lead.
A slight mishap saw Arruabarrena break to avoid a bagel, but Konta shut down any hopes of a comeback by seeing out the second set and the match.
On her performance, Konta added: "I felt I played myself more into the match a bit more. As the match went on, I felt clearer and clearer on how I wanted to play and what I wanted to do out there from my perspective.
"I'm quite happy I was able to execute that reasonably well. And also make it tough for her to stay in that match with the level that she was playing at."
Top seed Angelique Kerber barely broke sweat as she dropped just four games in a 6-2 6-2 win over qualifier Risa Ozaki, while second seed Karolina Pliskova did not have to work much harder to get past her fellow Czech Barbora Strycova as she came out a 6-1 6-4 winner.
RESULTS FROM THE MIAMI WOMEN'S SINGLES ROUND FOUR
11-Venus Williams (US) beat 7-Svetlana Kuznetsova (Russia) 6-3 7-6(4)
26-Mirjana Lucic-Baroni (Croatia) beat Bethanie Mattek-Sands (U.S.) 7-5 6-4
1-Angelique Kerber (Germany) beat Risa Ozaki (Japan) 6-2 6-2
12-Caroline Wozniacki (Denmark) beat 6-Garbine Muguruza Blanco (Spain) 7-6(1) 0-0 (Muguruza retired)
Lucie Safarova (Czech Republic) beat 4-Dominika Cibulkova (Slovakia) 7-6(5) 6-1
2-Karolina Pliskova (Czech Republic) beat 15-Barbora Strycova (Czech Republic) 6-1 6-4
3-Simona Halep (Romania) beat 14-Samantha Stosur (Australia) 4-6 7-5 6-2
10-Johanna Konta (Britain) beat Lara Arruabarrena Vecino (Spain) 7-5 6-1
Read the original article on Eurosport: Konta downs Arruabarrena to reach Miami quarters