I think your diary story is interesting, but you're playing with the time, right? Because Don and Cassandra are the same age, and Bella should have been an Elder if she hadn't disappeared. Sorry, maybe I'm reading too much into it.
...and Cassandra was kind of homely in the first game. In this game. It's easy to explain: Alex has Mortimer's skin and hair, with Cassandra's nerdy glasses.