What is the URL of the site in question? I'm afraid a google search only yielded the Kabalarians as citing Isia as a Turkish name. And the Kabalarians dont hold much water, unless you are into numerology or gerontophilia.
Isia may possibly be related to
Isa (which is also a female name) or
Isaiah (which however is a male name). I Most strongly suspect, however, that it is related to the Goddess
Isis. As a matter of fact, there is a classical Greek name Isia (or Isias) meaning "dedicated to
Isis. And in my book,
Isis has no unpleasant connotations :)