he sort of snapped- his sire owned a massive estate (aka downton abbey etc) and he basically was put to work after being changed and she took a lot of credit, put him in compromising positions one of which almost led to his demise and he wasn't good with that. but if she was in england around that time, if they were already friends he could've turned to her for help and did some sort of vow where they kept it just between them/came up with a story on how she was killed etc