[header] How to deal with a friend who's become an enemy [title] Pay attention to their opinions. [step] Friends will often share their opinions on a host of things, from your clothes to your significant other. These opinions come from a genuine interest in your life, whether it's good or bad. 
If your friend offers you constructive criticism that has a positive intent, that is acceptable. If they consistently bring you down with negative and overly critical opinions about you and your life, then it might be time to have a conversation with them about where the friendship is going wrong.