If this friendship is causing you to pull away from your faith, remember that your relationship with the Father is far more important than any other relationship you have here on earth! I used to feel like that a lot.
It may simply be a longing for the days where you two were still friends or when there was a group of friends who were close, as is often the way when you finally drift away from friends you made at school or university.
Rewind the clock, and when I was in my mid-20s, I learnt an incredibly valuable life lesson that despite the painful circumstances, provided a key period of in my life.