Dreaming about a close friend entering a relationship with her enemy could symbolize various underlying feelings or concerns. Here are a few interpretations to consider:

1. Conflict and Resolution: This dream might reflect your own feelings about conflict. It could suggest that you are witnessing or anticipating a resolution of some kind in your friend's life, even if it seems unlikely.
2. Concern for Your Friend: You may be worried about your friend's well-being or choices. If you believe that this relationship could be harmful to her, your dream might be highlighting your protective instincts.
3. Projection of Personal Relationships: Sometimes, dreams about others can reflect our own relationships. Consider whether there are dynamics in your life that feel similar, where you are concerned about alliances or rivalries.
4. Change in Dynamics: The dream could suggest that you are sensing a shift in how you perceive relationships, either yours or your friend's. It may be urging you to evaluate the complexities of loyalty, friendship, and rivalry.

Reflect on your current feelings towards your friend and her relationships, as well as any personal experiences that might relate to this dream. It could provide valuable insight into your subconscious thoughts and emotions.