Just like you, I have the kind of relationships with some Dommes that they are open and willing to discuss stuff like this. Based on these kinds of experiences and conversations, I would say that about 90% of Dommes experience some scary level of personal stalking at some point in their careers if they are active for a decent amount of time. By "scary level", I mean something that occurs that scares or unsettles the Domme in the same way that the Domme you saw currently is.

I actually think my estimate may be low but I know of at least one Pro (since retired) who was active for a little more than three years who this never happened to, so I can't say it is 100%. However, three different Dommes I have had more than just session relationships with have told me stories of how they have had to actually file restraining orders against a stalker and one legally changed her identity as a result of one (although that was well before I met her and may not have been specifically Pro Domme related).

Those are truly the worst of the cases but every Pro Domme I know that talks to me as a real person (rather than purely maintaining Pro/client distance) has told me some type of story like this. In many cases, it is because like your circumstance, they just need to talk about something that just happened. Even the one that I mentioned earlier that never had a scary encounter, had a guy who would randomly leave new shoes for her outside the dungeon. However, this confused more than scared her when it first happened since he didn't leave a note with them beyond "for Domme ..." and eventually it went from random to more of a ritual that he did a day or two before a session. Therefore, she wasn't surprised or scared when it happened (but someone less easygoing may have reacted differently).

This is the biggest reason why Dommes are rightfully wary about clients (even ones they have known for a long time) and interactions beyond the walls of the dungeon. It sucks for those of us that really like to get to know and care about them as people rather than just a provider of Domme services, but is completely understandable. All we can do is to show we actually care about them as women and provide emotional support if they allow us to do so while not being offended or put out when they don't.