Your dream is rich with emotional themes and complex symbols that reflect deep feelings of loss, love, and the desire for connection. Here are some insights into the key elements of your dream:

1. The Parking Lot at Night: A parking lot can symbolize a transitional space or a place of waiting. The night setting may represent uncertainty and fear. This could reflect your feelings about your friend's condition and your own emotional state.
2. Your Friend in a Coma: This represents a sense of helplessness in the face of a loved one's suffering. The fact that she may fall back into a coma suggests fears of loss and the fragility of life. It might also mirror your feelings of wanting to support her while grappling with the reality of her condition.
3. Memory Issues: The memory loss signifies not only your friend's struggle but also the impact of trauma on relationships. It may indicate your fears of being forgotten or losing connections with people you care about.
4. Overwhelmed by Medication: Your friend's choice to fill a prescription that could lead to an overdose indicates a struggle with coping mechanisms. This might reflect your concerns about how people deal with pain and loss, as well as your own feelings of being overwhelmed by grief.
5. Your Past Relationship: Sharing about your loss signifies your own unresolved grief. It suggests that you are grappling with the idea of moving on while still carrying the weight of past relationships.
6. The Offer to Buy the Restaurant: This could symbolize a desire for control and stability in your life amidst chaos. It may reflect your longing to create something meaningful or to establish a sense of purpose after experiencing loss.
7. The Final Words to Your Friend: Your wish for her to have something to wake up for indicates hope and the desire to provide support, even if it feels like you are losing her. It signifies your love and commitment, and it highlights the importance of having a reason to live.

Overall, this dream seems to encapsulate your feelings of grief, fear of loss, and a desire for connection. It may be beneficial to explore these feelings in your waking life, perhaps by talking to someone you trust or seeking professional support. This dream could also be prompting you to find healthy ways to cope with your emotions and to create meaning in your life, especially after experiencing significant loss.