This dream may symbolize a desire for closure and resolution in regards to a past relationship or unfulfilled feelings. The girl from your past represents a part of yourself that you were unable to fully express or connect with. The fact that you were unable to exchange a word with her in the past may suggest feelings of shyness or insecurity. However, in this dream, you are able to have a good conversation with her and work together on an assignment. This could symbolize a desire for communication and collaboration in your waking life. The fact that she is smiling and looking pretty may represent a sense of happiness and fulfillment in this interaction. The setting of your classes may symbolize a desire for growth and learning in this relationship. Overall, this dream may be a reflection of your subconscious desire to reconcile with this person and move forward in a positive direction.