Bella Goth

Bella Goth was one of the pre-made Sims shipped with the original "The Sims" game, in which she lived with her husband Mortimer and her daughter Cassandra. In The Sims 2, Bella no longer actually exists (as in, the Bella married to Mortimer doesn't technically exist, from a program point of view); however, her essence lives on in two ways.

Bella's disappearence from the game is a major component to the background story of Pleasantview, the neighborhood where her family lives. The story does not explicitly state what happened to Bella, although her husband, her children and Don Lothario have memories of her being abducted by aliens. Many of Mortimer's memories involve Bella, as do Cassandra and Alexander's. On the family tree panel, Bella's face isn't greyed out. This indicates that the game does not consider her to be dead.

Although the actual Bella is gone, Maxis created a likeness of Bella and used it as a townie in another neighborhood, Strangetown. This version is a little different to the actual Pleasantview Bella Goth, but is acknowledged by Maxis as the same Bella. The only way to send Bella to Strangetown (without messing up the game code) was to create a new Bella, so that's what they did! The fact that the Strangetown Bella has no memories of her loved ones or past life is simply blamed on alien experiments during her abduction.

Mucking about with the programming
Is generally not advised. Even moving Bella out of Strangetown gives a computer the equivalent of a migraine. Nothing special happens either - no tearful re-union, she is not acknowledged as Cassandra's mother nor Mortimer's husband.

Player stories
The player doesn't see Bella get abducted, but they know she is, as Cassandra/Alex/Mortimer's memories show it. She loses all memory of her family when she returns.