Insecurity Issues

Me(20M) and my gf(20F) have been in relation for 8 months. The problem is when her friends call her darling or say ' I love you '. She is laugh at it and I feel like she enjoys it . If her friends randomly beat her or push her. She just laughs at it and I said I am not comfortable with it. She says I can't understand the difference between friendship touch and other touch. I am feeling so insecure about it.. if it's my mistake, I like to change myself and become better. How do it? Please help out ur brother