Based on the idea that Trelawney is most likely her married name, it is quite possible that Cassandra Trelawney is the same person as Cassandra Vablatsky. Monkey-_ 14:30, June 11, 2011 (UTC)

No it isn't. Cassandra was implied to be dead in 1995, when Vablatsky died in '97. -- SaXon 14:53, June 11, 2011 (UTC)
If it is implied then it may not be the case, so my point still stands that they could possibly be the same person. Regarding Vablatskys death in '97, the chocolate frog cards were from the game Chamber of Secrets set in '92. This makes it a likelihood that Vablatsky predicted her death to come in '97, and somehow it came to be included on her card. As we know, divination and seeing the future in Harry Potter is a branch of magic that is seen as unreliable, so she may have predicted incorrectly and died in '95 or earlier.
The other possibility for Vablatsky and Trelawney being the same person, is that Vablatsky is obviously a famous witch because she has a card. Trelawney too was well-known as Dumbledore hired Sybill Trelawney based on her grandmothers reputation. Monkey-_ 21:28, June 12, 2011 (UTC)