I dreamed that my dead classmate called me and asked for a dream.

This is a dream of memories, in which she didn't die, so in order to convince you that she didn't die, she gave you an explanation and gained your trust. You have a good relationship with her both in life and in dreams, so in dreams she won't hurt you anyway. She called you there because you wanted to go there and improve this friendship again, but she has changed now. She has become a dead person. So the dream is telling you that nostalgia for the past is the essence and feelings of human beings and will not change for many years. Friendship is like wine. The deeper you remember, the more fragrant the wine will be. Although in dreams, people in dreams are also worth remembering. Although they are dead, their memories will not fade away. Live well, there will be more and more friends and better expectations. Trust your friends, too.