Has anyone else had a best friend change after getting in a relationship?

My best friend recently got in a relationship with a toxic guy, and it's really driven a wedge between us. He manipulates her and she can't seem to see what's really going on. I've noticed this happens sometimes with a lot of girls, when your best friend dates a guy and becomes different. (I.e. Starts to have this sudden distance/attitude towards you, is unable to be around you that much, excludes you and some of her other friends). And I just wanted to know if anyone else has been through this?