henrikegerman said: "I don't know the score - I know, I should! - but could it be that Helene - wrongly! - is affecting a three syllable word meaning "I am charmed" - akin to the "I am enchanted" of the three syllable en-chan-te? (yes, the correct word would be the two syllable char-me, but perhaps Helene is being vacuous or merely silly and inventive or perhaps that she's, though fluent, a bit of a Malaprop)"
I actually thought exactly this the first time I heard the song, like, 'oh ****, is there some verb charmanter that I've never heard of, and this is the adjectival form...?' That's exactly what it sounds like it should be, phonetically. But if this is what they were going for, it would be spelled "charmantée" in the libretto, and it's not. The libretto provided in the CD booklet is actually pretty good with its accents on the French words, IIRC, and I remember when I looked this one up, fully expecting to see something like charmantée, nope, it was written just plain charmante, as in the feminine form of charmant, as in the French word for, well, "charming." Which to me says it's the pronunciation that's off.
I don't have an answer for this question, really. All I know is that there's something weird about the French, be it by mistake or by intent.