I swear my rabbit is growling at me?

My pet rabbit is often let out into the backyard for a run around in a harness with a bell so we can hear where she is. Sometimes when I am putting food/water in the hutch, it sounds like she is growling at me and she runs at me and sometimes nips me lol, I don't know if this is because she is trying to get out, cause I often have to push her back in so she doesn't escape. I hope she doesn't hate me!