Your dream seems to reflect feelings of anxiety and pressure related to an important event, like your friend's wedding. The black silk dress you initially planned to wear could symbolize your desire to present yourself well and meet expectations. The fact that you cannot find it might indicate a fear of being unprepared or not living up to the standards you set for yourself.

The dress you find that resembles one from middle school may suggest feelings of nostalgia or a return to a simpler time when you felt less pressure. It could also imply concerns about how you have changed since then and whether you feel comfortable in your current self-image.

Running into another person who is also attending the wedding and seeking their opinion indicates a desire for validation or reassurance from others regarding your choices. The looming wedding time emphasizes your urgency and the pressure of social expectations.

Finally, the act of running through the city streets could symbolize your efforts to regain control over a situation that feels overwhelming. This dream might be encouraging you to reflect on your feelings about personal expectations, change, and how you manage stress in social situations. It could be helpful to take a moment to breathe and remind yourself that it's okay not to be perfect, especially during significant events.