Dreams can have multiple meanings and may vary depending on the personal experiences and emotions of the dreamer. In this case, the dream you describe can encompass several interpretations.

1. Insecurity in the relationship: Dreaming that your loved one is marrying someone else, in this case, a friend, may reflect feelings of insecurity in your relationship. You might be worried about the possibility that your partner may not choose you or that there is a lack of communication between you.

2. Jealousy and comparison: The presence of your friend in the dream may symbolize the comparison you make between yourself and her. Perhaps you feel that she possesses qualities you wish you had or that her relationship with him is stronger, which could generate jealousy within you.

3. Lack of communication: The fact that he did not inform you about the wedding may indicate a feeling of disconnection or lack of communication in your relationship. You might feel that you are not aware of what is happening around him.

4. Feelings of sadness: The sadness you experience during the dream and the "black boxes" could symbolize grief or loss. The boxes may represent unresolved issues or repressed emotions that you need to address.

5. Detachment or change: The black boxes could also symbolize change or the end of a phase. You may be processing the fear of change in your romantic life or the idea of losing someone you love.

In summary, this dream could reflect your concerns about the relationship, jealousy, lack of communication, or an impending change. Reflecting on your feelings and communicating openly with your partner may be helpful in addressing these emotions.