My 2 year old golden growled at me when I reached for her bone - totally freaked me out

So this just happened and i'm still a little shaken up. My golden Bailey has never shown any aggression in her life - shes the sweetest dog and loves everyone. But tonight I went to move her bone so i could vacuum and she actually GROWLED at me. Like a real growl, not a play growl.

Shes 2 years old, we've had her since she was 8 weeks. She's never done anything like this before. I know goldens are supposed to be gentle and friendly and this just felt so out of character. Should I be worried? Is this resource guarding? What do I do if it happens again?

I just want to make sure this doesnt escalate. My kids (7 and 9) play with her all the time and now i'm second-guessing everything.