I don't know. It seems like Olivia always had more patience with the Muppets than Maria.
Well, it seems like, compared to the other adults, she
really didn't believe in Mr. Snuffleupagus. In one episode, Maria hears Mr. Snuffleupagus talking as he drops off his toaster for her to fix, and when she tells Olivia, she doesn't believe it. In episode 1836, there's two scenes where Maria considers going to see if Snuffy is real, only for Olivia to talk her out of it (first when Maria hears Snuffy is behind Big Bird's doors, only for Olivia to tell her she doens't have time - by the way, why did Maria have to leave with Gordon, anyway? And then when Big Bird asks the adults to wait, Maria is willing, until Olivia points out that she'll have a long wait). And of course she didn't appear in the episode where the other adults see Snuffy for the first time.