So, I think this is a very powerful dream and it might stretch your mind some to consider the possibilities that it presents, so bear with me.

The dreamscape of a beach can represent the space between your subconscious self and your physical self. It's the border between the mind and body. Wind is the element of air connecting thoughts, ideas and words. This is the element that facilitates learning and contemplation. This dream space says to me that you were in a highly significant state of mind during the dream where you were meant to acquire important new information.

Very frequently people who have crossed over will make themselves available to us in dreams, to provide council, to offer comfort and even just to check in to let us know they are fine, and that they are thinking about us. This is an often reported experience called visitation dreams.

That your friend appears to you at an age similar to your own suggests that she wants you to take the dream seriously, as she demonstrated not just an image of herself you could easily dismiss as a memory, but as someone who aged right along with you. Plus she probably wants you to understand that the message she conveys isn't based on something an inexperienced 18 year old might come up with. She has evolved and grown, as have you.

Of course I would agree with you that although you cannot recall the conversation she very likely intended to ease your mind about death and the transformation that entails. You may be able to still retrieve this conversation if you have a practice of meditation, or if you simply relax into a reverie state and recall to mind the dream as vividly as you can. Walk yourself through the memory of the dream and allow it to unfold as it will. You very likely will be able to hear or understand or retrieve the message as a result.

Hope this helps.