I read it twice.

And the second time, I caught it — the flaw, sitting right there in the middle of her indignation, plain as a dropped stitch. Valerie. I had never spoken that name to Rosalind.

I had spoken it only to Brandon, on the phone, hours earlier.

Which meant Brandon had gone straight to his mother and told her that I had found out — and which meant that Rosalind already knew exactly who Valerie was, had known all along, and had helped him carry the secret.

Her own careless use of the name had confessed it for her.