It's actually pronounced Seew-Anne, or that's how my history teachers pronounce it. Llywelyn The Great had a daughter or a sister or a wife called this.
It's pronounced 'shoo-ann', this is my name! I am quite offended by these comments. This is no place to call names 'Retarded'! But at least I don't have a boring name like... I don't know... 'Mary'?