What does it matter? The he-said-she-said around the mahogany table is always a loser.

However, it is company supplied material as they loaded it onto their entertainment system what they deem appropriate material for semi-public viewing. WRT to a coworker, she initiated her presence within your static personal bubble. As a professionally trained employee she is fully aware of this dynamic. Unless you forcefully held the screen up to her face saying, so waddya think? I'm not sure what could be done.

I would be more concerned about the litigious parent who says you irreparably harmed their child especially since they know the employee's company has very deep pockets and that company can be easily identified because you were "in uniform, and in public view" (as you say) and presumably know better (the lawyer will say) than to expose minors to porn, regardless that the scene was sudden and unexpected. People love to sue big companies.