As stated above, it may take her becoming a victim to realize that something could happen to her. Hopefully it will not.
Ten years ago, my wife was totally against me getting my CCW or even having a gun in the house, despite the fact that she had been robbed at gunpoint in south Tulsa (before we even met). Over the years she has come to terms with the fact that I take my duty to protect her and my family seriously and that firearms are part of that.
If it causes tension between you and your sister, just talk about something else.
Ten years ago, my wife was totally against me getting my CCW or even having a gun in the house, despite the fact that she had been robbed at gunpoint in south Tulsa (before we even met). Over the years she has come to terms with the fact that I take my duty to protect her and my family seriously and that firearms are part of that.
If it causes tension between you and your sister, just talk about something else.