I was tempted to say it's Corinne Hermès, but then I thought you'd choose someone even longer ago, like from the 70s.
Then I thought it was Geraldine
She really looks a bit like her, but she's irish....
so...
my next guess was Monique Melsen, but apart from her having darker hair, she's one of the true luxemburg singers who represented their country.
The others from the 70s are either male or I know their current look, so it must be someone from even before.
Is it Michelle Torr? She has some similarities...