I was browsing through some porn sites at home last night and came across a videoclip. It was around 2 minutes long and uploaded one day ago. From what i could see, it looks very much like her. I've never talked to this female colleague before, so i'm not sure how to bring it to her notice. Also i'm not completely sure that its her, more like 80/20. Its really bugging me. If its not her and i tell her about it, i may get in trouble. If its her and if i ignore it and she comes to to find out about it after few days, it maybe too late for any damage control. I'm really confused. What should i do?
It sounds like you are okay with ignoring it and letting things go, which I actually think is the right choice in this instance. However, if you were more confident it was her and felt the need to tell her, I would do it anonymously.
Create a sock email account and send her an email from a concerned acquaintance. For example:
I am an acquaintance of yours and stumbled upon something I thought you should know. Not too long ago I found a video on a porn site that looks very much like you. The video looks like it was taken surreptitiously, so I was concerned that you didn't know it existed. Hopefully this isn't actually you, but I thought it better to say something and be wrong than to remain silent. I chose to remain anonymous as I do not know you that well and do not want to create any awkwardness between us. You can find the video at this site under the title XYZ.
Sincerely, A concerned acquaintance
If you only have her work email, be careful about sending porn links to her office account - you don't want to get her in trouble. If you go this route, just make sure your tone is considerate and to the point. If the video is her she will already feel violated and doesn't need it enforced that you recognized her backside.
The fact of the matter is that is has nothing to do with you.
The person in question may be happy with it on-line. Porn is made by real people and they do have acquaintances. So is this a "scandal".
So you wish to go to a stranger and say "I watched porn last night and I liked/disliked your performance on this site".
Just do nothing.