You’re right. Someone who was present for all of the Freighter/Falcon stuff was a major leak.
The shot of Maz handing someone (previously presumed Leia) the lightsaber wasn’t in the film, was it? They used a different shot, and it was Rey. Makes sense as I’m sure they were no where near finished with Maz and needed something that obscured her. Still, why show it during ‘my sister has it’?
I remember some versions of the leaked outline had Maz accompanying Han, Chewie and Finn to the Resistance base. It’s possible she was supposed to give the lightsaber to Leia at some point.