Or "To you the glass is three-quarters empty, but to me it's a quarter full."

See the discussion box.

Substituting one song for another won't work, because this is subtitles. And people won't understand the cultural reference if you do a literal translation, so I think you need to invent some lyrics to the French song.

My idea is to make up your own song.
The original song goes "tout va très bien (four syllables), so, "I'm sure you're fine", in a teasing manner, then tra la's, or something similar.

I would actually advise against finding a different quote if you can, as the intention of the line will come across directly through the literal meaning of the words, and the tone in which they are delivered. If it's important that the audience understand this is a reference from a song, then the style guide you're using will likely have a suggested font for indicating quotations and lyrics. (See if there's already an official translation of the song if you haven't already :) )

If you'd like a more technical explanation of my thought process here, it involves a bit of translation theory, and whether or not we ought to 'bring the text to the audience' or 'bring the audience to the text' (a somewhat reductive approach, but something I still find useful to keep in mind). The choice here is, however, a little less tricky than it might be if the quote were otherwise.

Because the reference is highly French in the first place, the anglophone target audience will have to either already know the reference, or else miss that it is one in the first place. But because the quote and it's intended meaning for the scenario at hand are directly translatable, I would leave it alone. If you change the quote, a lot about the context changes, and the reference loses it's 'originally intended meaning' anyway. This will be a translation choice which has to either value the tone of the passage or the fact that a reference is being made. If the reference is more important, don't change it (in my opinion), but if the tone is more important (nostalgia is at work, specific cultural context is at play) then maybe something everyone knows (like the Beatles) could work.

In my opinion however, changing the quote is a lose/lose, and I would translate it directly.

My take on it.

Used in the US too. Maybe the expression is a little aged and out of date and usage, like the French one.

"Stiff upper lip" I was thinking of too, but that's probably too English.

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Note added at 12 hrs (2021-05-03 22:57:40 GMT)
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https://www.collinsdictionary.com/dictionary/english/ladyshi...

Used in Co Cork, Ireland, humorously but not maliciously, about girls and women who have got "notions" or are prima donnas, to bring them down a peg or two. If memory serves.

I think it's a good fit for "Madame la Marquise", because presumably Madam isn't a Marquess at all...

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Note added at 12 hrs (2021-05-03 23:01:19 GMT)
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Oops, sorry

marquise nf (titre nobiliaire) Marchioness, Marquessa
La marquise est l'épouse du marquis.
The Marchioness (or: Marquessa) is the wife of the Marquis.

https://www.wordreference.com/fren/marquise

Bonjour,
Je viens de trouver la traduction anglais de la chanson de Paul Misraki. Tom Lerher la chante en Anglais. Le terme que vous cherchez fait partie de ces paroles ; le lien est dans les réferences web ci-dessous. / I just found the English translation of Paul Misraki's song. Tom Lerher sings it in English. The term you're looking for is part of those lyrics; the link is in the Web references below.

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Note added at 4 days (2021-05-08 03:11:06 GMT)
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Please ignore the comma after Madame la Marquise. It was that way in the lyrics and I accidentally copy-pasted it with the term.