Good/bad news for you, then: that's not her real house! Your first 5 villagers always have a boring generic default house that's set for their personality--everyone's first peppy has the same super pink house with a bunk bed, for example, instead of their real house they'd have gotten later, and everyone's first jock just has terrible bland wooden stuff with a punching bag. Everyone's lazy has a dirt floor and my starter uchi, Reneigh, also has the house that looks like a bad version of Bob's. :/ One way you could fix this is by trading her to a friend and then having that friend trade her back to you, and she'd get her real interior and also still remember you.
I agree with you on Muffy, though! She's not a fave of mine but she's still pretty cute, though to be honest the sheep are one of my favorite species and imo they all got downgraded in NH by being put into shirts that look too small for them.