Trying to imagine what would bring together a corporate employee of a tenant of an office building and a person (possibly recently hired?) as a 3rd party contractor security guard for the building, not for her company.
It's one thing if they both worked for the same company -- even if they weren't both working in the same type of work.
But the security guy she'd most likely encounter on her way into work, out to lunch, leaving for home?
Was DS a smoker smoker? It seems unlikely, given her healthy lifestyle. but a lot of who eat right/exercise still smoke cigarettes. Seems crazy, but people do it.
Cuz then she could've seen him when she went out for smoke breaks (which you dang smokers do a lot, makes me jealous).
Does that office building have a gym on-site? Many do nowadays. Not great gyms, but serviceable.
Or an after-work spot in the building/nearby where people go for happy hour? He could've chatted her up there.
Difficult see his personal life outside of work being on her radar. Unless he had something to entice her, I suppose.