How to convey that the POV character *does not understand* what's said in dialogue?
The general advice is often to focus on the content of what's said in dialogue and just write it in the reader's language, largely whether the characters would use that language or not in-universe. See for example the answers to this recent question or for that matter universal translators.
However, what if you really want to show that the point-of-view character does not understand what the other characters say? As he or she sees it, they are speaking to each other, but the words are gibberish.
In the particular case I have in mind it's a made up language, but it could just as easily be a real human language.
Obviously one shouldn't overdo it (there's a reason why the general advice is for the author to translate, and I mostly agree with it), but for something like a few lines, is it acceptable to make up some such dialogue or should I just stick with something like "she looked at him and spoke in [their native tongue]; I had no idea what she said, but [the result was ...]"?
Put another way, in what situations might it be a good idea to actually write down the actual words, rather than a translation into the reader's language?