I don’t believe anything that Burrell says. He’s a shifty slimeball. I reckon the only conversations she would have had with him would have been work related.
All this rock stuff is utter fantasy on his part and she wouldn’t have treated him as a confidante. She was brought up with staff and would have behaved accordingly with her own. Also she would have had the measure of him.
Granted, he may have overheard stuff and had unparalleled access to her life, but that’s as far as it goes, in my opinion.