that reason is because she was your sister and you can't get over her death or because she was really really close to you and you loved her more than anything.
You were having a horrible nightmare
The dream expresses the dreamer's own grief and distress. The subconscious mind produces the dream in an effort to make sense of the senseless loss.
Sometimes dreams can tell us lots of things. From my investigation every time we dream, our sub conscious travels. When we dream we dream of many things like, places, ocean, people, or flowers. The reason why you dreamed about your classmate who committed suicide is maybe you were thinking of that person. It could be that you missed that friend because it's your school break. Nothing is wrong with you, nor something bad might happen. It's natural to dream the person that we knew esp. if that person is not with us anymore.
Sister Sister - 1994 I Have a Dream 5-18 was released on: USA: 25 February 1998
The meaning of the dream depends on its emotional tone (fearful, happy, sentimental, etc.) as well as the content and context of the dream. For example, a dream about watching the sister drive away in a car would be very different from a dream of baking cookies together in granma's kitchen. Very generally, the dream expresses the dreamer's own feelings; it provides no information about the sister or her feelings.
This dream suggests that the dreamer feels a sense of guilt concerning the sister. The dream is not predicting any future event.
This dream reveals your feeling that your sister-in-law is interfering too much in your marriage.
The dream is showing you how the broken relationship with your sister is "stealing" your happiness. The image of your sister in the dream reflects yourself. In the language of dreams, you see yourself burglarizing your own valuables because of a value-less disagreement.
The dream means that your mind is trying to tell you that it is time to let go of the past and to contact your sister. This dream provides a fine excuse to open the channels of communication.
In this dream, the "sister" represents an aspect of the dreamer's own personality. The kissing represents discovery or "getting in touch with" that part of the self.
Dream On - 1990 Sole Sister 1-4 was released on: USA: 29 July 1990
It probably means that your sister has been giving you a hard time.