It's not the first time this has happened, she also breached impartiality rules three years ago:
Martine Croxall: BBC News presenter breached impartiality rules, corporation says - BBC News
https://share.google/WSV4JyH6T7jEmGa0Z
Going on to joke about breaching due impartiality rules shows what scant regard she has for them.
Someone has said that she might be a union rep, I wonder if this has afforded her greater protection than other staff?
When I worked in local government I was asked to consider becoming a union rep and it was said to me that, unless I did something like murder a colleague, I would be unofficially exempt from any form of disciplinary action. I assumed that this was because the council wouldn't want to risk any industrial unrest because the union would view this as an inflammatory act by council management.
Perhaps it's the same with the BBC and Croxall is fully aware of this??
The first time I would have expected her to receive a verbal warning, the second time a written warning and, if she does it again, she should be dismissed.
As we come up to charter renewal and the BBC is under unprecedented attack for accusations of bias and the TVL method of funding, they need someone like her like a hole in the head.