Complex sentence: The whole conflict around the Regency led to a serious discord between the Prince of Wales and his mother, who in an argument accused her of having sided with his enemies, while she called him the enemy of the King.
Split into simpler sentences: The whole conflict around the Regency led to a serious discord between the Prince of Wales and his mother. In an argument he accused her of having sided with his enemies, while she called him the enemy of the King.