I think that sadie will be fine with another dog you should have nothing to worry about when i first introduced hunter and daisy they loved each other right a way now when we go outside and daisy trys to get into hunters pen we have to stop her because hunters gets exited and is so big and would probably jump on her by mistake so they play with each other through the fence and when we take daisy back inside hunter crys like a baby and just looks at the sliding glass door until we come out again