I'm sure some people will respond soon with suggestions to help with your issues with Maggie.
A few things that would be helpful is to let us know what you are feeding her now. Food can have a lot to do with issues that bullies have in particular.
The mange is likely because her immune system is compromised from the kennel cough. Getting her on a good food or supplements that will help build the immune system can then help fight the mange I believe.