If the origin is unknown, how can the name have a "meaning"? Or at least, the meaning given would be metaphorical or mystical and have nothing to do with etymological history.
Anyssa is best thought of as a simple spelling variation of Anissa. This may be simply a name created by blending sounds from names like Anna and Melissa, or perhaps is a variation of Anisia, (Greek “fulfillment”), the name of a saint martyred in Thessalonica around 300 A.D. It's unlikely to have an etymological connection with "star flower."