Amanda was wrong by the Graysons. She switched identity with someone named Emily, so she could come back and plot revenge against the wealthy Graysons. Amanda now goes by the name Emily, and she has become independently wealthy. Amanda bought the beach house next to the Graysons to plot revenge.
After several months the Grayson son Daniel fell in love with Amanda, and they get engaged. Meanwhile, Emily has come to town raising hell (posed as Amanda), and the Graysons are worried that she is out for revenge. At the engagement party, Daniel is shot. The Graysons believe (reasonably) that Amanda might have something to do with it (or was at least on the beach) the night Daniel was shot. They were even right about the person they thought was Amanda. She was on the beach. But they were also accidentally right about Amanda Clarke being on the beach that night, because she was posing as Emily.
So this looks like a case of justified true belief that Amanda was on the beach, but it’s not knowledge. Now I have to think about whether this has any interesting consequences for candidate attempts to solve the Gettier problem. I have some thoughts but I’m going to sit on them for a minute and think about this more.