Complex sentence: This angers the Snow Queen, who is watching the children from her mirror, which she smashes with her scepter, telling the ice splinters of the shattered mirror to go into the eyes and hearts of those who have offended her.
Split into simpler sentences: This angers The Snow Queen, who is watching the children from her mirror, becomes angry and she smashes it with her scepter. The ice splinters of the shattered mirror to go into the eyes and hearts of those who have offended her.