Any uncles or fathers of friends maybe? My mom was the same way. Once I turned 19 she didn't have as much pull in my decisions. I never shot a rifle until I was 19. I'm now 35 and she still worries about my bro and me. She always will and so will yours. You will probably never find a way for her to feel safe with your hunting. You have to prove youself always. Hunter safety is the first step. I don't mean to bring you down, but some people never feel good about firearms. Good luck with your situation.
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SweetInnocents