I think she is baptising the roses, with the contents of the [champagne ?] bottle. [Don't know, do roses like that, champagne?
]
Or maybe she shares some knack of her mother about roses with the other persons on the picture. [Look, my mother always told me.....]
I have seen pictures of Queen Paola baptising a rose with her name, but it was clear that she did that with water.
Anyway I like it to see that also a princess happens to water plants as I often do, most of the contents of the bottle goes next to the flower pot.