Should advice be give or to just stay silent when a friend complains about a guy who doesn't want her but she still defends him?

In such situations, it's often best to listen empathetically rather than immediately offer advice. Your friend may need to vent and process her feelings without feeling judged. However, if she consistently defends someone who isn't treating her well, gently encouraging her to reflect on her feelings and the relationship might be helpful. Ultimately, being supportive and non-judgmental allows her to come to her own conclusions.