Hi Chris,
Sorry, my mistake, I thought that what you meant by "expressed an interest", was that Susan had initiated a contact with you through Genes Reunited. I thought you had received a notification email but wasn't aware that you could, even as an unpaid member not only read the message at the board but reply to it.
Very sorry to give you false hopes but a couple of people I contacted through GR were not aware that even as non paid up members they could reply to me. It took a two or three tries on my part before the penny dropped.
Not sure if there is a way for you to make contact as a non paid up member, it might come down to sitting back and waiting for Susan to make the move. If you have her surname you could try a Google on her name, she might just be on another board under her name.
I only rejoined just recently, I received an email from GR of some "hot hits" on some of my ancestors. Two people even had my gt grandmother in their tree, so it became worth my while to rejoin and make contact.
Just a thought, if you let me know her full name I could see if I can contact her to contact you.
Good luck.