I am getting stuff off the websleuths forum that this Wendy is saying that Karr told her the Ramsey's had a open house and that Karr went to it and toured the house during this open house.
Where I live they do open houses at Christmas time, so that people can view the Christmas decorations. The house does not have to be historic or old.
He told her details that were known to all the JBR case followers.
She was not a JonBenet Ramsey case follower - she was interested in the Polly Klaas murder. She didn't know these details were already well known.