Contrary to the rest of the World, Disney does not think boobs are something we should love to see.
That's the uncut footage from "All the Cats Join In", one of the best segments in "Make Min Music".
In the version released on DVD that's what we can actually see.
Notice how they did not magically deleted the girls' breast while she is undressing, and a mirror separates the eyes of the audience from her, but they deleted them when she runs out of the shower and dresses herself.
More seriously, at Disney they were scared to death by the fact that this girl is in her teens, and under age, so they felt it was unappropriate to show her naked breast.
Can you imagine the Fleischers thinking something like this in the early Thirties?