My long distance GF called me and told me that she wanted to go to concert but none of her friends of family could go except her guy friend she met 4 months ago. I’ve never met him. I told her I don’t feel comfortable going one on one to a concert with a single guy formed she has only known for a few months. Anyways she ends up going and she is saying I’m insecure and jealous. 

I’ve been dating her for 8 years and although we have some trust I feel she is using this “you are insecure card” to walk over me and do what she wants. 

TLDR- am I the asshole for not being comfortable with my gf going to a concert alone with a single dude she met 4 months ago?