Now this seems to be an interesting book you are referring to. Could you give us the quotation in question? What exactly does it say? Yes, too bad it doesn't give any references.
A friend of mine has access to "Paulys Realenzyklopädie der classischen Altertumswissenschaft". He promised me to look up
ALEXANDRA. If there is any evidence for what you claim, here it will be found.
Pausanias obviously doesn't say anything more than he has found people worshipping a certain
Alexandra (or knowing of her), who is in fact
Cassandra. He dos not say, why they call her A. of from when on they have been doing so. So I would say, he is a bad witness in that respect.