I was struck seeing this post on instagram because I spend A LOT of time thinking about this very construct, and I love that it was liked by Bernadette and Audra.
Of course, I absolutely agree that Sondheim has Bernadette as his unique muse (Sunday in the Park, Into the Woods, Anyone Can Whistle, Evening Primrose tracks with Mandy, Anyone Can Whistle, Gypsy, A Little Night Music, Follies, Old Friends, her Sondheim etc. concert that has she has essentially been doing a US and world tour of for 30 years, plus readings of Bounce, audition for Sweeney movie as Lovett etc.). Angela Lansbury likely a close second (Sweeney, Gypsy, Whistle, A Little Night Music).
HOWEVER, I don't know whether to clutch pearls or not that it is in fact Liza associated with Kander and not Chita.

If I recall, in their book 'coloured lights' Kander & Ebb talk about Liza and Chita at the same tier. Believing both can do anything.
Liza did Flora, Chicago, The Act, The Rink and the 'Cabaret' movie.
But Chita did Chicago, The Rink, Kiss of the Spider Woman and The Visit.
Did LMM get this wrong? 

Videos