I looked and couldn't find a source. And so with this in mind I'm going to call it for what it is and say that it's most likely a hoax.
As for Lita is a ph.d, I have no clue who she is. Though one would think that information such as silver toxicity paralleling mercury would prove to be far more significant in the Colloidal Silver usergroups than with unsubstantiated or isolated statements such as these.
That said, I'd say there is far too much factual information under the tenets of scientific research to credit such claims as anything but a hoax at this stage.