How do you tell your friend you think her boyfriend is using her?

Okay so...first off, you call your friend and tell her that you need to talk to her. Don't make it seem like you are going to talk to her about this issue...just hanging out. Then when she comes you should talk to her about how much you care for her and how much you know what's best for her blah blah blah. Then you should say as your friend, i need to tell you that I think your bf is using you. But, you need to make sure you have proof otherwise she won't believe you. Then, just talk to her about how you think she should break up with him. If she really is a good friend that she will listen to you. But, if she's a loser then you know she doesn't trust you, and she is not a good friend.