It can take a month or two for the fur to fill back in depending how big the bald patch is. Having her in a small cage probably isn't doing her any favors and probably causing her some stress, why not put the fleece in her normal cage if you want her scent on it?
Lack of stimulating toys can also contribute to boredom, and over grooming as well as being alone. The new pair will probably help providing they all get along etc..