Cinderella means something like "girl dirty with ashes" and is an expression that originated from the famous fairy tale of Cinderella.
The first time this expression would have been used was to name a famous Italian tale, which would later inspire Cinderella's story, called: La Gatta Cenerentola (“The Cinderella”). The bubbles are the ashes of a fireplace. In English, "cinder" is a small piece of burned wood, and is one of the products of a fireplace or fire, along with the ashes. Often "cinder" is even translated as grey. The name Cinderella comes from there.
Currently, Cinderella is considered all girl who works incessantly with domestic services, either on her own or by being forced into it.
This meaning arose precisely because Cinderella is a "cinderella cat", that is, a young woman very beautiful who had to submit to forced domestic services, always getting dirty and unwell dressed.
Borralheira is the name given to the place where the ashes or rubbish from the wood ovens (rubber) were kept. They were pretty dirty places.
In short, the Cinderella cat is a beautiful young woman, but who lives in the middle of mess or dirt.
In Brazil, this expression is also commonly used in the sense of “messy girl” or “confused girl”.