If you know the language they’re speaking (and your narrator knows) you could do something to the effect of:
Her English melted into German, a quiet muttering as she talked herself through the delicate process of rewiring the circuitry into something that would serve their purpose all the better.
It can be quite a different story when you’re writing a fictional language. It really depends how in-depth you want to go, and whether or not your languages have a name known to the narrator. For one of my works, there’s a period of time where the narrator doesn’t know what language certain characters are speaking in, so I tend to announce it in such ways as:
Whatever language he was using, it wasn’t English. | The sentence descended into something nonsensical… etc
When I’m writing from the perspective of one of my characters who speaks multiple non-human languages, I have gone that whole extra mile of nerdiness and created the languages for him to speak in. He’s pretty fluent in the languages he has a command over, but there is an instance where he’s in an area of his home world which he has never visited before, so his grasp of the language is extremely formal and unusual to the ones who live there.
So I tend to just have him say something in the language he knows best, and write it out. You can see a little example in this drabble-y thing I wrote a short while back if you have the inclination.
Otherwise, please see below for more resources to help you out!
I hope this helps.