You can’t be the only one she’s blabbing to, so just tell the people she’s blabbing about! They might be angry enough to report her for you!
And, what do you think she’s telling them about others? You?
She may even be breaking privacy laws, so….
Easiest thing to do is tell her she probably shouldn’t be telling you, as it’s probably illegal and not very professional. What would happen if any of them found out you could tell them to the penny what redundancy someone got, or the debts of someone else….not that you would, of course!