It sounds like the dog is asserting herself & viewing herself as higher in the "pack" than you are. This may be because you weren't involved in the initial training & obedience work, or because you do not have a dominant body language. There may also be (real or perceived) nervousness, apprehension or fear on your part when giving commands & reprimands.
This type of behavior is often seen between the dog and children in the family. They key to changing this behavior is to work on basic obedience commands, with proper rewards.
What you have tried so far (spanking & time out) is not effective, and likely wasn't administered properly, which has made the behavior worse. Especially considering the breed, if you physically tried to correct behavior, the dog probably viewed you as not in control of the situation, and decided to take the upper hand.
Because the behavior has escalated to growling I strongly urge you to get professional advice from someone in your area. If possible, you & your roommate together should take the dog to an obedience class & work on basic manners. Find someone that works with a positive reinforcement method.
Additionally in the home, stop using the word "no". It doesn't mean anything to the dog. The advice I gave my husband so he understood what to do with our dogs is to give an 'obeyable command'.
We use a sound to get the dogs attention (think of making a buzzer sound, agh agh!) and then the command. So if the dog was chewing on the furniture, it would be sound, then "leave it". As soon as the dog stops chewing on the furniture, an immediate praise is given "good boy!" or "yes!".
Now, if the dog still had its mouth on the furniture, but halted the chewing, the praise was still given, and if necessary, followed with a second command, such as "come here", which when the dog leaves the furniture & comes towards you, more praise is given, both verbal & petting, or maybe a treat.
This type of positive reinforcement teaches the dog that #1. you are the one in control & #2. doing what you command results in good things happening.
In the same example above, lets say the dog was not stopping the chewing behavior. With puppies, I would suggest physically removing the object, but you are dealing with a dog that has already exhibited growling behavior, so instead find a substitute, such as a bone, & offer it to the dog. As soon as the dog takes it (redirection of behavior), the praise is given.
The key to this type of training is #1. Always give an obeyable command. "No" means nothing to dogs, and becomes noise after a while. #2. Always always praise! If you are telling the dog to do something (which is the same as telling it to not do something else), then you must let the dog know when it did the right thing!
Even if the dog doesn't change their behavior on command alone (such as offering the bone to stop the furniture chewing) still reward the behavior, because the dog did make a choice. Think of it as the dog learning to read, it needs to memorize the letters first before it can make words. Eventually, the commands will start to make sense, & the dog will become more willing to perform them for you, in order to get your praise.
Some common commands that we use in our household:
"Leave it"
"Come here"
"Go away" (which really means, go leave this immediate area, usually given with a sweep of our hand pointing away. Great for getting a dog to stop begging for food! Say it nicely, in the same tone as the other commands)
"Bring it here"
Once you have begun incorporating this change in behavior correction, you should also work on basic obedience commands:
Sit, Down, Stay, Off (Off is for off the furniture, or no jumping, Down is strictly for laying down)
We have our dogs sit & wait for their food (fed 2x a day). If your dog has food always available, you can do this with a treat instead. Sit & wait to be released, with your release word as being "OK!" followed by praise & petting. Practice different lengths of time, from just "Sit... wait... ok" to a 5-10 second wait before release.
The goal is to have the dog willing to respect you in the household, and follow your commands without dissent.
I am a breeder trainer owner of Rhodesian Ridgebacks since 2000, & draw on my experience & knowledge to help others. All advice given above is simply that - advice. I have not met you, or the dog, or seen the interaction & behavior, and as such, the situation may be more extreme & require further intervention.
Again, if possible, go to a trainer together, or at least consult with a trainer on your own. Be safe, and if you have any specific questions, do not hesitate to send me a message.
T. =-)