There are many Eight models, and although many answer to 'Sharon', they are each individuals. (They are similar to comparing Data to Lor in Star Trek: TNG). They were the last model created by the Final Five
and the most human.
Even though they are the same 'model', they have different personalities, traits and romantic interests and friendships.
Boomer was involved with Chief Tyrol and #1, where as Athena married Helo and had a daughter (Hera). Boomer died a final time on the basestar in the final episode and Athena settled on Earth with her husband and child, getting her happily-ever-after.
In issue nine, Boomer and the Returners return to the Cylon fleet, only to be shot down by their own. Before being resurected, she has a dream that she is the "original" Sharon, a human, and she teached a group of other Eights what that means. This gives a great insight into the false memories the Eight models have and explains why they have more feelings then the other 6 Cylon models.