I am very happy to see her with such precious jewels, I like her taste in jewellery.
The Nassau sapphire tiara looks nice with blonde hair and she has a good way to wear delicate jewels,not only on her wedding day but also for Estelles christening (pretty pearls!). As I am not a fan of big show-off pieces,I enjoy her accessoires and how discreet they are.
With the last gala appearance I think the problem is that the dress does not photograph well,such glimmery-shiny materials looks much better in real than on the pictures.In a shop I have seen the dress from Elie Saabs collection where it looked very pretty.
To me it looks beautiful how Stéphanie wears this special sapphire tiara,it is nice to pull back the hair to give full view of this beautiful gem,however I agree with other posters that the colour of the stone is a little bit difficult in combination with the colour of the dress.A pale (diamond?)stone tiara would have looked a tad better IMO,but I am very happy with her recent gala outfit.