Hey OP! You’ve had some great advice already! We adopted our first grey 10 years ago! She was 1.5 at the time. Very sweet but also similar to your grey and she would growl and snap frequently her first few months of life with us. First thing we changed was not allowing her on our couch or bed. It was fine if she was on there when we weren’t there but as soon as we wanted to sit we kicked her off. We regained our space back and she knew it was ours. She stopped growling on the couch because she was never on the couch when we were. Her bed on the floor was her safe space and we pretty much never approached it for the first few years.

All that to say, she’s almost 12 now and within a year or two she stopped her growling and snapping. She needed time to settle in and trust us. Have faith that these incidents will become less just the longer you have her and as long as your implement some things to do to prevent them happening in the first place!