Is it normal for my friend to do these things?

Here is the story
So I have this friend and we have a group together and we hung out everyday during the summer and became extremly close...well at the time she was single...well we began highschool and she met a guy her and the guy slowly started dating until the were official. I thought nothing of it at first in fact I felt happy for her. But as time advanced I started noticing her not wanting to hang out too the point where I was a complete back up plan. She was also straight edge and her boyfriend was into drinking and smoking which gradually influenced her choice too sell out..I want to know is this normal behavior too toss aside friends for a boy? Also she dropped out the last quarter of school. I wanna help her but I'm afraid I can't influence her.