I have a question about Bella's behavior lately. She is aboug 15 weeks now, and I think she is starting to show a bossy side... when I comb her she has been growling

. I don't comb her rough, and try not to pull too hard, but she growls. Also, I tried to put her shirt on, and she got mad again and growled a little. Any advice on what to do to stop this. Also, do you think I have something to worry about for the future? Thanks!