"she didn't like being called a potential security risk"
She's clearly the kind of person who likes to take offense then. I would interpret "Discussing the potential security risks with Noreen." to mean having a conversation with someone called Noreen about potential security risks, not about potential security risks of someone called Noreen.
Though if I were Noreen (which I'm not, except on the weekends) I'd be more confused as to why as a new starter someone wanted to discuss security risks with me.