Complex sentence: Her magic mirror is a portal to the magic mirror world, where she talks to a much younger reflection of herself (played by Lisa Roberts Gillan), and the reflection often warns her not to use her magic for selfish short sighted purposes.
Split into simpler sentences: Her magic mirror is a portal to the magic mirror world, where she talks to a much younger reflection of herself. The reflection often warns her not to use her magic for selfish short sighted purposes.