Tu est envoutante
is one way of saying it
Vous êtes trés belle/jolie
It may be not be weird if she understands French, but her national language is Slovak.
"Belle femme" is "beautiful woman" in French.
Belle famille is beautiful family in French.
Beautiful skin in French is "Belle Peau" :)
'Beautiful view' translates to French as 'belle vue'.
Belles personnes is "beautiful people" in French.
Beautiful photographs in french is de belles photos
Beautiful all over in French is belle partout.
Beau Rêve = Beautiful Dream
You say, belle cousine.
cloche
belle