Bonding Exercise-Works well for young pups
LOL!! I had the same problem with my pup at the same age, she's a rott/dobe. My trainer has told me that this specific breed are well know as "talkers". What you might be interpereting as growling may actually be "whispering", barking, growling, sighing, crying, their all just ways that dogs influctuate their voice to be understood. I wouldn't worry about it just yet, but there are some bonding exercises that you can do to ensure that she always knows your in control
1. Tell the pup to lie down on her stomache, straddle her, and massage her shoulders and neck firmly. If she tries to move tell her sternly "Your fine". Move over her face, touching her nose saying nose, touching her ears saying ears, teeth, eyes. etc. (This helps with vet checks!!)
Part 2. Lie her on either side without allowing her to get up and feel her side and legs check her feet. Repeat for other side and do not allow her to get up until you let her. Not only does this strengthen the bond between you and your pup, it gets her used to people touching different areas of your body. You can also easily detect if there is a lump or something odd that shouldn't be there. Good luck! And let me know how it goes!