You're not on your own on this Mr S. I find this a peculiar and ambiguous situation. Trouble is that whether true or not, or irrespective of test results it'll remain so as the strains of herpes virus resulting in cold sores are carried by substantial numbers of the general population.
There's nothing further from the OP (on this or any other WG) but even if he tested "positive" it couldn't reliably be linked to this WG unless he'd had a "negative" result on the same test just before meeting her.
Unless there's any further information you're just going to have to make your own mind up about the balance of probability and go with your own estimation of risk. As I've said previously I would require a proper good look at her in full light before proceeding, but that's my stance on any WG (and expect the same from them; after all I do fuck around).