I think she was present judging by the second picture on Instagram.

From the Princess Foundation website:
On Saturday 12 December 2020, the traditional Christmas Ball was held in the Salle Empire of the Hôtel de Paris under the high patronage of HSH Princess Charlene of Monaco and in the presence of Mr. Gareth Wittstock, Secretary General of the Princess Foundation Charlene of Monaco.
Bal de Noël 2020 - Fondation Princesse Charlene de Monaco

So under the patronage of Princess Charlene but in the presence of Gareth Wittstock. If Charlene had been present the Foundation would have said so.

Thank you, I do speak english but the woman who appears in the second picture looks very much like Charlene.

Yes, I also thought there was a very strong resemblance as well. Yet, with further information about Charlene being with her family and no actual mention that Charlene was there on the Foundation website it would be nice to find a more definitive disclaimer that she was unable to attend vs deciphering the language on the website and enlarging photos.:rolleyes:

This ball has been around for a few years now and I think PC has only attended once.There's pictures from it every year and I'm always confused as to why she's never there as it's under her patronage. When you enlarge the pictures it's clear the woman in black isn't her although it does look like her from a distance.