Complex sentence: Apparently, he had a disagreement with his mother, a domineering woman, over him having a girlfriend, who later remarked about Shrubsall's lack of remorse when he confessed to police.
Split into simpler sentences: Apparently, he had a disagreement with his mother, a domineering woman, over him having a girlfriend. His then-girlfriend later expressed concern about Shrubsall's lack of remorse when he confessed to police.