How on earth do I handle this woman?!

[GreyjoysAnatomy]

Background-

I have two best friends, one of them (A) has a friend (B) who she recently introduced me to. Seemed nice, been out for coffee together a few times, all fine. B added me on Facebook a few weeks ago, no problem there.

A few nights ago B messaged me asking who my other best friend (C) was from my wedding photos. I said "oh that's C" thinking nothing of it. (C has a very distinctive haircut and people often ask about it so it didn't seem strange that she would)

Since then she has been repeatedly messaging me asking if he's single, sending me lingerie photos of herself (bleurgh) to show him etc. I have politely told her he's not interested and she seemed to get the message and stopped.

But she's messaged him!! He is really creeped out by this weird stalker lady (as am I, I barely know this woman and she's sending me semi naked photos ) and has blocked her, naturally.

What on earth do I do about her? I can't just not see her, she's going to be at an event next week that I'm attending and I don't want it to be awkward for A.

Aibu to think she needs telling to back the fuck off?!

[GreyjoysAnatomy]

UPDATE

The event was last night, she did mention it and I just told her I wasn't comfortable with her sending me photos and I'd prefer not to discuss my friend at all. She seemed a bit put out for a couple of minutes but didn't mention it again and soon was back to chatty.

I'm relieved it's done with now, no awkwardness, and I don't have to socialise with her often so that is fine. I am concerned about her home life though, and after a chat with A, A is going to keep an eye on her as we both agreed it was an odd thing to do and she may need a friend. Hopefully it's nothing bad going on in her life!

Thanks for all the advice