I find the OP’s story very plausible, and think all the rebuttals are unconvincing.
ISTM that the premise underlying all the suspicion is that the whole idea of these videos is no big deal to begin with, so if you could “refute” them being you then all is well (and a further assumption that the woman herself knows this to be a widespread attitude).
However, as Loach observed earlier, this is not the reality of most people’s mindsets - agree or not, most people would be extremely distressed at having video of themselves masturbating distributed to their friends and relatives etc.
Further, it’s extremely common for faked pictures, or even video (e.g. “Obama kicking in the door” comes to mind), to circulate on the internet, and fool quite a lot of people. You get all these discussions with experts and self-declared experts debating back-and-forth whether this or that picture is real or not, with in-depth analysis of subtle signs this way and that way. If someone sent out photo-shopped pictures of someone else masturbating it’s very unlikely that their friends and relatives etc. would analyze it in enough depth to determine one way or the other, and in any event many people tend to be taken in by these, as above.
I myself have never engaged in any online chats with any female strangers so it’s not like there would even be any basis for someone to tie something like this to me, but if someone would contact me with a threat to distribute photo-shopped pictures of me engaging in sex acts I would not be pleased. I’d like to think I would resist blackmail under any circumstances and especially dubious circumstances like this one, but the facts are that many people are willing to pay up to blackmailer, and it’s a reasonable shot for a scammer to take.
And it’s not like every scam is based on a coldly calculated and accurate assessment of the likelihood of this or that scam working. People are thinking of this in terms of some vast business enterprise headed up by a shrewd big-time scammer, but it might be some pathetic amateur down on her luck and looking for cash for her next fix, and trying something similar to what she’s heard of other people pulling.
Bottom line, again, I think the skepticism is unwarranted. Of course, you never know, as with everything else posted to this or any MB.