So I messaged this girl on OkCupid saying:

"okcupid says we're a 72% match. I don't know how they determine that, but I saw you like salsa dancing and that's definitely a match in my books. I think that justifies a cup of coffee at some point next week.
- KRB"

She replies saying:

"Hey KRB, we've actually met in person before at the [a friend's house]. I used to know [personA] before she left the country and then came to know [personB]. Remember me at all? " (personB happens to be a common friend of hers and mine)

Now I did not remember this girl ONE BIT, so I wrote back:

"Quite surprising we know the same ppl, small world. So why'd you stop going to [friend's house]"

and her response was:

"If you don't remember me in person, you probably don't want to date me. Best of luck on OKC. "

So now where does this go? is this girl a dead end, or is this a shit test to see if I buy into this frame of "oh no, please don't leave, I want to remember you"?

help would be appreciated

She is just baiting for some validation. She's bitter about the fact you don't remember her. I'd just say "People change, for better or for worse " and let her interpret that however she wants to. Then ignore that subject and carry on with the conversation.