I disagree that this is what is happening in this story. Just because she's considered herself straight her whole life doesn't mean she can't discover she's not now. And if a hot coworker confessing to her is what it takes for her to go "hey, maybe I do actually like women too" then so what? Everyone's journey is different. Some people just can't imagine how they'd feel about something until they are actually in that situation.
I remember hearing a story about this actually happening to a 40-year-old woman.
It's nowhere near as big of a shift as realizing you're gay, but something similar happened to me. I realized, years after having met a person, that I had a crush on them since we first met. It was just after hearing they had broken up with their long-time partner. I realized it, and then realized I had been subconsciously avoiding thinking about it until that moment.